can we make it work and be happy?

this is long. but i need to know. so me and my boyfriend of 6 years, 3 kids together, just got back together after 2years apart. i want to know, do you ladies see any possibility in this that we can get past it and make it work somehow, can we be happy together at last. so, 2 years ago, i found out some girl was about to give birth to my boyfriends baby. they have a daughter. just after she was born, me and him remained together, but unbeknown to me, he was still seeing her behind my back for months, before me and her then got talking and she told me. he sat me down and admitted, that hes in love with her, ans not in love with me. and we parted. they ended up in a realtionship together. at this point me and him only had 2 kids together. our two sons. and while with her it was like he dropped us to the side. didnt show up for them. wasnt around as much but during a visit one night to see the kids etc we slept together. and it resulted in me being pregnant. AND HER. so we both ended up oregnant with girls. but he still stayed in a relationship with her. ans stood by her pregnancy leaving me to do mine alone. was at there daughters birth. but not ours. at times during my pregnancy he spoke to me like i was shit. ans treated me like shit. which wasnt the man i knew. so after my daughter was born i lost loads of weight, and met a nice man. we only dated a few times. if im honest i still loved my ex ans was hoping to make him jelous. and things between him and her werent good because he also cheated on her with me and got me pregnant so she had trust issues real bad. there relationship hit bottom. and xome new years this year when she was asleep he wouldnr stop ringing me that he missed me. she found out in december shes pregnant again with his third child to her. but they are broke up and both cant get along anymore. he has told me hes taking no involevment in this pregnancy or with the baby. and he hasnt seen there two girls in a few weeks. things got worse between them becauss just after easter i got a text from her to say she has just found out hes back with me and she wants me to be aware they have slept togsther on 3 occasions lately. she sent me texts to prove its true. but hes still insisiting shes lying. im so torn and dont know who to believe. but i really do want to try and make this work. and now that they hate eachother and dont speak i dont have to worry now about them doing anything. but i really need advixe. is it possible to make it work and be happy. we did spend the first load of weeks back together fightinf and arguing but she was still kind of on the scene until now. i really want it to work. her baby is due august. will he likely stick to his word this tims ans take bo involevment. he said the last two years with her was a mistake and he finally realises where he wants to be.