Help me. I cant move on from my ex, i feel addicted to him and cant let him go. What should i do?

Hello,

My ex broke up with me last december (we stayed 1,5 years together), the break up was traumatic with a lot of highs and lows and i cut off contact definitly end of February. Before i cut off contact , I did everything I could to make him stay , i begged , i wrote letters. Some days he was like ok im givin you another chance and some days he was just really mean to me. He blocked me everywhere, i was really really hurt. I felt like i was dyin. So i cut off contact and he didnt try to contact me neither. 

 I met a nice guy in march and spent a lot of time with him, we kissed and became friends. I was getting better but suddendly at the end of April i started to miss my ex a lot again. So i folded and contacted him again. We met and hooked up. After this meet up , he didnt contacted me. Two weeks later, i wrote him a long message and told him i still loved him and i want to try again. He was really mean to me and said i should go to hell. But suddendly after one week he messaged me and told me he just want to meet me for sex and nothing else.  I was really unsure at the beginning but I agreed. I thought that maybe if we have sex more often he would fall back in love again (yes i know its very stupid to think that). Almost three weeks long, we met almost everyday to hook up and he was really kind, he bought me chocolate, stay to talk and he was joking with me.

After three weeks i needed to go home and see my family. The last night with him was really special we were laughing a lot and we had breakfast together. I decided to confess my feelings again and he rejected me. I went home but i couldnt let him go so i was texting him a lot and trying to convince him for another chance . His answer was cleary no. I was really sad about it and i asked him maybe we could stay friends with benefits. I dont know why i did this, but i was desperate to keep him somehow in my life.

He agreed but afterwards he began to ask a lot of questions about what i did after our break up. He asked me if i slept with someone, i said no. And suddendly he got very upset and accused me of lying and cheating even. That he knows that i slept with different men and he saw me. But its impossible because i didnt do that, so i was very confused. He got mean again and said he changed his mind he doesnt want to see me anymore. I became desperate again and sent him long paragraphs to explain that i didnt lie or cheat and i dont want to lose him. You know i want him to be nice, i want him to believe me.

He got distant and took hours and to even respond one message. So i was thinking like i cant leave the situation like this so i texted him a lot of messages again. One time late evening he was super responsive and even nice. And the day after he was like ok we can stay friends with benefits but im still believing you're a liar and a cheater.  I didnt understand his reaction, i was upset and said how could he even sayin this stuff. He left me on read, so i send him again a message in which i apologized and i said i was happy that we could stay fwb and he left me on read again. So i sent again a message and asked him why he is leavin me on read and he still didnt answer.

I got really sad and upset again. The issue is I feel like I need to let him go and dont care about him. But i cant and its drivin me crazy that hes leavin me on read. I mean he can just answer "i dont want to talk to you right know" and it would be ok. It triggers really something in me and I dont know what do. How to let go ? How to resist the urge to sent him messages ? How to leave him behind? Does anyone has any advices?I would love to take them. I feel like addicted to him.