What can you do if you can't move on from someone and you keep breaking no contact but they have no problem losing you like you never mattered?

I have been crying for days and I feel like I'm losing my mind over this guy and I can't go on a day without crying. We've been dating for 9 months and although we weren't exclusive, we were loyal to each other for that time period. I have never loved anyone as much as I did him. We started dating just a few months after he and his ex broke up I believed that he was not going to use me as a rebound because I felt like he really loved me like his feelings were genuine. My relationship with him had its ups and downs, we fought at one point but I did not expect that that was enough for him to lose all his feelings for me and just drop me like I meant nothing. Now I feel like he's made up with his ex and now he just wants to be friends. I told him that it's not easy for me to just be friends with him since I'm still attached to him and it's not easy for me to get over him. I feel so used. I tried to go no contact but I keep breaking it and messaging him about how this entire thing hurt me because it's like he doesn't care. It's like he doesn't care if I got hurt. I gave him every ounce of myself, all the attention, all the time, and love for it to end up with him not wanting me anymore and for him to be okay with us not talking, for him to lose me. I don't know how to get over him. I feel so hurt and it's consuming me every day and him not caring makes it 10x worse. I want to get over him for my sake because I feel miserable very single day I don't know how to keep no contact I keep going back to him.

What can you do if you can't move on from someone and you keep breaking no contact but they have no problem losing you like you never mattered?
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