Am i evil??? i'm seriously attracted to my little sister!

I don't know WHAT to make of it. She's my half sister. I'm five years older than her. We were very close when we were small, but I joined the military at 18, and we didn't actually see each other almost at all during the time I was in. We talked on the phone and/or emaied each other maybe about once a week, or every other week while I was in. Anyways, I did my four years, and got out, and have been out about a year. However, my last few months before I got out, she was like SUPER excited about me coming home! Since I got back home, we see a LOT of each other, and she's always telling me that she has really been missing that closeness we had.

She REALLY grew up a lot while I was in, and is an extremely beautiful girl, drop dead gorgeous by any standards, but I NEVER had any sick thoughts or intentions or anything like that. She's always been very affectionate person, and I like that about her, so for her it was never a big deal to like hug and kiss me, then sit on my lap.

However, that was a problem because... whenever she did that (sat on my lap), for SOME REASON, I almost immediately got a hard-on. At first, I just contributed the phenominon as a normal physical reaction to her body weight/ pressure to THAT area. But, I would get it almost every single time!

Then, one weekend when I first got out, my Mom and Step dad took us to a cabana club, with pools, jacuzzi's, and sauna's. My mom called us out to go grab something to eat at one of the tables. We were both soaking wet, and she was in a bikini, and I sat down, and she sat on my lap, and very quickly I got so hard I thought it might burst. I pretended that I had to use the bathroom, and almost literally ran away! In the bathroom, I found that not only did I have possibly the strongest erection of my life, but even worse, there was also a very small amount of seepage. I felt HORRIBLE, and could not get my erection to subside.

Everybody was cool when I got back, and just wanted to know if I was feeling well. I faked an upset stomach, and everything was ok. After we went back in the water I tried telling myself not to worry, but when were back in the water, looking at her in her bikini gave me another erection! Her body all wet and glistening in that little bikini was messed me up so bad, I had to get out of the water (wrap a towel around my waist), and tried not to think!

The experience was so scary for me, that I immediately get up, and do something the moment she sits on my lap to eliminate that problem; which works. And, within a month after "bikini day," I got an apartment with a friend of mine as a roommate. I figured my best solution was to just create some distance. My sister was really upset I was moving out! And, kept telling me how mom said, it was fine for me to stay, and that I don't have to move out, or even pay rent if I stay. She made a BIG deal out of it, and didn't understand why, I told her that I just needed my own space, and that she could see me anytime she wanted to.

And, a month later... she got a car! She practically moved in, and the erections have not stopped. She doesn't even sit on my lap anymore, I just get them around her. Especially if she wearing short-shorts, or something. Two weeks ago, she was wearing a tight top, and some short athletic shorts while painting her toenails, and I had to leave the apartment! I thought I would get over it, but I haven't. Its actually gotten worse. I even occasionally, have erotic/wet dreams of her. Moving out did create some distance, but I'm not sure that even helps. She's here a LOT, but usually sleeps at mom's house. But, this past week she wanted to crash at my place.

She didn't want to sleep on the couch, and thought I was being ridiculous when I began setting up to sleep on the couch. I have a full size bed, and we could both fit. I knew it was probably a bad idea, but I really didn't want to explain why, and I didn't want make it a big deal. So, we fell asleep, and somehow ended up spooning. And, I guess at some point, I ended up feeling her bottom up on my area, and I woke up because I felt something, almost kinda like "gyration?!" I woke hard, and on the verge of release. She was still asleep, so I got up and moved to the couch. Then, she woke up like five minutes later, and wanted to know why I got up. I said, that I just need more room to sleep, but it seemed weird because the couch is kinda small. She seemed upset, and It was mad awkward after that, but she stayed, and didn't leave me alone the rest of the following day.

And, just to amp up the crazy, my roommate who I've had almost a year now, is leaving, and my sister wants to move in! She's working now, and keeps telling me paying half the rent won't be a problem, So, now I obviously have to find a way around that!

Then, I start thinking that I'm not even sure that its all me anymore, because she goes thru my phone sometimes, and makes these little innuendos. Plus, a gf a few months back, approached me saying, "why does your sister hate me?!" When I approached Tiffany about it, she got defensive, and acted like my gf was crazy; which makes me think.

But, then I'm like hold up.... wait, and I can't believe I'm trying to put THIS on her?! I'm the messed up one, its like I'm trying to share the blame to make myself feel better or something; which is even more twisted!

I had to catch myself blaming her, for what goes on in my crazy head. But, then I think back, and some stuff she does sometimes seems weird, like she's teasing/tempting me on purpose, and I have to stop myself again, but I keep thinking like that. Even though I know she wouldn't do something like that, especially because she doesn't even know! I can't even imagine the devastation it would cause if she had any idea! I know she really loves me, I can't imagine the damage that would do. And, obviously I love her too, but I just can't get the poison out. Even when I think I have, she'll do something, and it comes right back!

I don't even know what's going on anymore! Sometimes I feel like the only solution is to re-join the military. It just sucks though because I don't want to go back in, and I'm finally going to school like I wanted. But what else can I do? Sit my sister down, and tell her I can't ever see her again because I think I want to have sex with her??? Yeah, not going to happen!!! I don't think there is a 12 step program that deals with my problem. And, it really sucks too because I DO really enjoy her company, and she's an awesome friend!!! And, I miss her when she's not around. Am I crazy?!?!?! Am I just a horrible person?! Should I be on pills or something?! Its weird though because I don't feel like I'm crazy, so am I just evil?! I mean, I have NEVER once touched her inappropriately, or initiated any kind of questionable interaction, that has to count for something...right?!?!?!