I (19F) am becoming distant and toxic toward my (19M) boyfriend. What should I do?

I really don’t know what is going on with me. I feel that I am becoming very distant from my boyfriend. Whenever we hang out I have a snappy attitude, I don’t give him as much attention as he gives me, sometimes I just don’t feel the same connection I used to at all and I truly don’t understand it. Tonight he brought up something that was bothering him and I quickly got very defensive, but I never notice these things until the damage is already done. I know I sound like a horrible person and I really really feel like it too. I love him so much and he is kind to me and I want to be with him, I don’t understand why I am acting like this but I hate myself for it and don’t know what to do. Sometimes very tiny things he does make me incredibly angry for some reason. I know these are signs that our relationship is heading towards a breakup but I really don’t want that to be the case. I just want to know why I’m feeling this way and why I’m acting like this. I know that nobody can really give me an answer to that… IDK. We have been together for 2 years. Does anyone have any advice?