Why can't I fr love another person

It's just I don't GET myself? I mean I know it's hard to let go and it takes years to move on but I tried to have new lovers and like this year alone I alr went with like 4 ppl and they would only last like few weeks. The longest one was 2 months All I could think about is always my dead ex-bf and he wasn't even healthy for me </3 the reasons for breaking up is like because I'm still inlove with him... I tell them beforehand tho that I'm having a hard time moving on because technically we never broke up. I gave up on love life and just be single.