Is this healthy and is it normal?

I've been in a relationship for 5 years. We both have 2 kids from previous relation an 1 together. I've loved this man since we were 13 (25 now) but we never clicked then so we just hung out went to movies really good friends. then finally before my 20 birthday we got serious but he was still seeing his kids mom any anytime I showed dislike i him taking his kid an kids mom to the movies he'd get offensive an not talk to me for a month. finally after getting fed up with him takeing day trips to other cities with her an out to eat all the time I stopped talking to him then one day he calls me up crying because she wont let him have his son cause he wont take her to get her nails done an explains to me he wants to be with me but she gets jealous when hes with me an keeps his son from him. So after getting shared custody an working on us after a year were finally doing good but then my sons dad gets jealous of how much time were spending together an asks to keep my son for a month. Seeing no problem in this I agree.. an much to my dismay my son passes away in a fire at his dads. In emotional shock I block out the world an have been very depressed ever since but a not even a month after my boyfriend leaves for an ex an after finally getting over him after wanting him around for emotional support hes finally gracious enough to grace me with his presents again an ofcourse like an idiot I took him back an now its been 4 years... no indiscretions but still I cant trust him and I'm always scared hes going to leave me an I hate that I cant trust him to go to his mothers (ex lives across the street) or pick up his kid or even go to work an it's driving me insane. I've been on prozac an talk with a therapist to'try an learn to trust' him again but I cant an I think about all the wrong he's done to me an it makes me depressed all over again an I want to leave him but I cant bring myself to do it. why? advice please someone. should I stay or continue working on us for our family/kids?