Why did I do it?

Hi, I need advice and help.

I was in a two and a half month relationship, we faught but we where so in love. Or so I thought. I never realized how much I was draining her. We had this big fight that broke us up. For context, she has this besfriend that she used to like, well the girl has a boyfriend. But she likes my gf, well ex gf now, and it bothered me so much. She told me not to worry about it and she wouldn't do anything to hurt me, but ive heard that so many times that trust is just so hard to have in this world. Well my ex ex gf from like a while back, we stayed friends, well she told me that my now ex gf was gonna take her bestfriend to prom instead of me. Now I have issues with controlling my emotions, things I say, and how I react. SO I got mad, didn't think, and we'll called her. We argued about it. Later on after give us about two hours to calm down, I find out she's on the phone with that bestfriend!? But I tried to fix things so quickly. She got even more mad at me. Wouldn't listen. So we just stopped talking and said that we just need to wait for the morning to see what to do. We went to a break for like the first half of that school day, got into my 2nd block class, got a break up message. Now here I am about two or three weeks later, she's been making me so confused. I kissed her even Though we're not dating!! She didn't kiss back but she never stopped me. It's happened so many times now. What's happening. Am I just a toy? I'm confused, this is killing me. It's like I wanna leave, move on, and go back to the me who would've immediately moved on. But I'm