Relationship advice.

I am 23 yrs and been with my bf for 5 yrs with 3 babies in heaven. We have broken up many times and im getting to the point where i just dont know anymore. Everytime I leave I come back. I just know i can be happier with someone else so why is it so hard to leave for good. I dont know what to do. He is not a person I feel like I could marry any. He has no motivation and weed takes up his life he loves being at home with mommy and doesn't wany any responsibility I want my own house with someone who wants the same things I do and he just wont step up. Please give me your opinions. Thank you.