I’m so hurt

My bf and I have been together for a year and four months. He has two children with another woman which I knew about when we first got together. We moved in together after 6 months of dating. He tells me he loves me and calls me beautiful every day. He tells me he wants to have my children and marry me. He even does that thing where he stares at me like he wants to be with me forever. BUT I've seen messages of him telling his baby mom the same thing. Him saying that he wants to be with her. I confronted him about it in the past the first time it happened. He said he only says those things to keep her happy otherwise she would use his kids against him. Which I get because whenever she's mad at him she threatens to put him on child support. My thing is I love this guy so much and I've done so many things for him and this is the second time I've caught him messaging her in that way. We ended up breaking up so they could try again even though he still stayed with me. I asked him was he just using me the whole time and he says no he really loves me and he tries to keep everyone happy. We ended up getting back together and he never told her. I told him I still would have helped him with anything he needed he didn't have to pursue me just because we lived together we could have stayed friends. I just don't understand how he could have done this to me when I was there when he didn't have a place to stay and was broke. I never left him. It's hard for me to do it now but I know I need to.