Is it normal that i hate pda?

I'm a Senior in High School and I can't stand it? Like, sure, it bothers me when I see people swapping spit and shit in the hallways, but I hate it even more when people try to get me to do it? It was one of the reasons why I broke up with my ex, because he always wanted to kiss, hug, hold ends, etc. but I'm not like that. It really makes me uncomfortable. As for sex, it's something that I have fantasized about, but when I actually picture myself in the situation I get grossed out? It's just, the act is nice, but actually having to do it with someone else physically turns me off.

There's also the fact that I'll have a huge crush on someone for forever, but when we actually become a thing it's like all my feelings I had for them just go away, and I don't know why, and it makes me feel guilty, because here this person was who liked me too, and the second we're a couple I just have no interest whatsoever. That is, unless it's over the Internet, but in real life I can't hold a relationship where we're physically together. I mean, I'm bad to the point where whenever I went with my ex somewhere I'd always ask my friend to tag along because I'm really shy and awkward. It's really embarrassing because I'm so introverted and it's terrible that I can't even go on a date without having a friend to come along with.