miss him like crazy! help!

I was with my baby's dad for 5 years. Then things got rough and we went our delegate ways. He gets his daughter every couple days. He does have a new girlfriend which was his girlfriend before we got together. They are having a baby now I guess. But the last couple days I've missed him and cried so much. I don't like the thought of him being with someone else, sleeping beside someone else, doing things for someone else, caring about someone else. I don't know if this is just a phase and I'll get over it or if I should talk to him about it.