Why am I like this?

I have a son with my boyfriend. I’m 20 he’s 21. I’m not affectionate. Don’t kiss me, don’t hug me, don’t grab my butt or boobs, or smother me. I try to be nice but I can’t🙄 I get so annoyed with any touch unless it’s sex but right after just leave me alone. I used to never be like this. Ugh. I love him I just don’t know what’s wrong. (We’ve been together for almost 3 years)