Help me !!!!

I just don’t know why he feel as though he can walk in out my life. I think I love him but I don’t know. I never did anything wrong but be there for him and care for him. He was my first love...my first everything. But he would just do something weird and stop talking to me and then come back into my life. I don’t know what to do. Cuz I don’t see myself with nobody else but him.