TW: mention of self-harm

I (19m) have been talking to this guy (19m) for about 2 months now. We were friends/aquaintances from uni before and then we started flirting. In the beginning, I thought he was really awesome and I was impatient to find out how much he likes me. 

I haven't been in a relationship before so I tried to take it slow but I asked him eventually and he said he liked me but didn't know how much exactly and thought I was awesome, but didn't know if he wanted to date a man and he'd only recently broken up with his girlfriend. I misunderstood him and thought he didn't like me at all which really upset me and I'd already been struggling with thinking I hated him/he hated me before. I ignored him for a while and then told him I didn't want him to continue flirting with me. But the next day I asked him about it again and we decided to keep flirting and talking (I felt like he really understood me). 

But since then it's gotten a lot worse. I have bad mood swings and some days I feel incredibly anxious, others I just want to never talk to him again and some days I enjoy being liked back by someone for the first time. I tried really hard to keep it together, there have been a few days where I ignored him and a few times I self-harmed to not lash out on him. I also tried to make him jealous because I felt jealous because of him talking about his ex so I told him about a girl I had liked and hurt badly in the past and that I still missed her. I know that I shouldn't have done it, but I couldn't help it.

Today I felt really bad and hated myself a lot, so I decided to reach out (I'm not good at asking for help). I told him that I wanted to be someone else and he asked me why. I told him that I felt like a failure, felt bad about how I've treated other people in the past and hated how I took everything so personally. I said that maybe I'm just really stupid, incapable or lazy. He said that he thinks I'm a bit lazy and that really hurt my feelings. I'm struggling with my mental health and I suspect I might have ADHD (I'm on a really long waiting list to get checked) so I'm not really able to study a lot which makes me hate myself. I wanted to be comforted, but he made me feel worse. I felt the urge to tell him I hated him (I didn't, I ignored him instead) and now I just want to not talk to him again, at least for a while.

Am I being irrational by feeling so hurt? I'm so confused by my feelings and what I want, I don't know what to do anymore. I don't know if I'll go back to liking him again, if I should tell him that I can't do this anymore or just stop responding to the flirting. Can someone give advice?