Stay with boyfriend, or be with babys real father??

Ok this is a looong story so I'll try to make it short. I need advice because my mind is going back and fourth. My boyfriend and I have been together almost 5 years, with alot of problems, and lies from his part . We took some time away from each other , but stayed living together. During that time I saw a coworker, I'll call him Steve, and ended up pregnant by him. I told my coworker about it, he said he wanted to be involved in the baby's life , he has 2 kids of his own with his ex. And then I told my *ex* boyfriend and he said that he loves me and wanted to stay even though its not his. He stayed with me the whole pregnancy, and when baby was born. His only condition was to tell steve that it isnt his, and to erase him from my life and the babys life. The problem was I didnt want to erase steve, he knew the baby was his, and knew I was lying when I told him it wasnt his. I had alot of feelings for him , he finally made me happy and always makes me laugh. Steve insists every single day he wants to be with me and raise the baby , who's now 3 months old, and that he loves me so much and wants to move in together. We arent doing anything together, but I do keep in contact about the baby. My boyfriend does not have any kids of his own, and told me he loves this baby like his own ..But our relationship isnt good at all.. I feel miserable with him, he doesnt make me happy, we havent had sex in over a year even though he insists all the time Im just not attracted to him anymore. The only reason Im still here is because he wants to raise the baby as his own, and he doesnt have any other kids , I just feel bad that he has been raising him for 3 months, then I just take the baby away forever. And a huge part of me wants to try to have a family with steve because he makes me happy and finally feel good about myself.. I dont know what to do