I don't know how to move on.

I'm 22 years old, I know I'm still young and have my whole life ahead of me but this guy I met 3 years ago has really caused me so much pain and hurt. We started dating in 2013 and he left me in 2014, met someone new and until this day is having a child with her. Through everything I still communicated with him. I just feel so stupid because I know i deserve better but yet I continue to go back. I know it'll prob never work because she has his child. But this is who I'm used to. I feel stupid for still being around after all this. And I just don't know what to do or how to let go. I feel like she's important to him and I'm just somebody he deals with when he wants and I also don't understand how she's the only female but when I try to move on he's calling, popping up at my house, etc but yet treats me like I'm nobody. I'm a good person besides my attitude being bad but I don't feel like I should be treated this way by anybody. I love him but I know it's not healthy.