Is it normal for my girlfriend to start being awkward with me?

I dunno, maybe she already cheated, and is already feeling guilty about it? Then again, maybe not, but you never know.

She:
... admitted to liking another guy.
... is gradually reducing communication with you.
... seems upset and refuse to tell you why.

Yeah, a break up is coming soon. It's not your fault, and you didn't do anything wrong. Along with that, the other guy isn't better than you. Your girlfriend is just naive and getting toyed with by a player, that's all. Even if this wasn't a long distance relationship, there's nothing you can do.

I know it may not seem like it, especially after all the years you spent pining after her, but this is a blessing in disguise, because if she's easily manipulated, then it's better it happen now than years down the road when you're married or have a child with her. Also, you're very young, and you seem to have a good heart, if you date wisely you'll definitely find another woman worth your time and effort.

She just doesn't sound interested anymore.

She's probably banging some other dude, only read 5% ot your op

It's over. You're 18, so you're at the beginning of your college experience, which means you have 2 or 3 years to go. She already figured out that by staying committed to a long distance relationship she isn't going to have any fun. There's a guy giving her attention, and you keep bugging her over texting and Skype, cimg across as needy and distrustful. It's pretty much over.

So you have three options:
(1) Move back with her and do online college or go to college close to her if she still wants to be committed to the relationship.
(2) Have a long distance relationship but accept you two will see or date other people. Fair is fair. But don't bring not up now; bring it up after you have seen her and are back to college.
(3) Move on.

Now, you have to realize you can't be doing the same crap you've been doing. So here's what you have to do:

Without being drastic or calling attention to it, text her less and Skype less. Less time, less frequently.

Stop talking about the other guy and asking her about him... you're coming across as insecure when you need balls of steel.

When you see her, just have a great time. Focus on her having fun instead of talking about the relationship.

For now, find a female friend and potential replacement near you. It'll give you some emotional stability.

Realize she maybbreak up with you on January when you see her, so think about how you will handle that. It may be at the beginning or toward the end.

You're worried about losing her? Mate, I'm really sorry to say but you've already lost her.

Im shocked, you say your in college, but yet so many spelling errors.

She is too passive aggressive to tell you she is dumping you. Find another sex partner.

Mate,this little birdy already cheated on you and something tells me deep down you know that.You were just hoping we'd give you hope that she hasn't.Just grow some fucking balls and ask her what the fuck is going on,let her come clean and allow her to go wirh a clear conscience.After all,things like love can never be forced and no one rules their heart...only their actions.Cheers noogie.

Based on how you describe her behaviour it sounds like she's cheated already or is thinking about cheating on you. Long distance relationships almost never work.