What’s wrong with me??

I’ve known this guy for years and he asked me out at the end of March. We dated until August when he broke up with me because he could tell I was distant and not as involved as he was. We agreed at the beginning that it wouldn’t be anything serious because neither of us have really dated before but he got way more serious than I ever did. I don’t know what my issue was but as soon as I started dating him I hated him. I didn’t initiate conversations, the thought of hanging out alone with him made me anxious to the point that I couldn’t do it unless there were other people around. I didn’t want to kiss him, and I hated talking about our relationship to other people. It took me until June to talk about it to my parents. I care about him a lot and I just don’t understand why I had such a fear of dating him, or anyone really.