obsessed with childrens father

My childrens father and I were together for 5 years, when he started accusing me of cheating, which I never did, he was the one cheating and everything that he accused me of was something that he had done throughout our relationship. Because of these accusations the relationship turned emotionally verbally and physically abusive. Hes not a bad guy & this abuse is totally out of his character, but he ended the relationship and I cannot let it go. I'm obsessed with it, I can't sleep because I dream about us, when I'm awake I cry all day. I don't know how to let this go its been about 5 months & I'm still hurting terrible, I thought we could be friends and still hang out but I don't want to just be his friend I want to be with him, Should I seek professional help because I feel like I'm going crazy?