I think a big thing for me was crushes- everyone else always seemed to have someone they liked (except for me). I also just had a general disinterest in being in a relationship. Any time someone said they had feelings for me, however infrequently it occurred, it made me really uncomfortable.
Adding on to that, there was a guy back in third grade who said he liked me and would occasionally bring me dandelions during recess, etc. Then it started being more borderline harassment; he would follow me around and stuff. So, naturally, I punched him in the stomach.