23Bisexual

I admit that i am serial cheater wherein i always cheat everytime im in a relationship. Recently i got engaged but before that I was in a relationship with another girl and my ldr boyfriend came home proposes to me. 

I tried to fix my relationship with my boyfriend but the reason why i stayed because we have a child and I don't want to have a broken family.  I can feel that i really love the i girl that i was with but I can't stay for her because of my child.

Any advice