I don't know what to do...

So we've been together 11 years, married for 6 with two kids, aged 4 and 1, with another due in February. He works long hours and I'm sahm (which I hate but it's our only option right now). I have complex PTSD, depression, anxiety, fibromyalgia, and I carry a genetic disorder our newest is likely to inherit. I've cheated twice and he's forgiven me. We don't have sex, for a while now, because of me, I just don't feel "it" anymore. What I'm trying to say is, I'm the problem, and I know it. During an episode earlier this year I tried to get him to leave me, told him every horrible thing I've done and begged him to leave me but he wouldn't. His parents were together until death and that's what he wants but I really believe he can and should do better. I don't think I'll ever be "right" again, I don't think I'll ever want sex again, I am never going to be what this family deserves and I just want to get out of their way. If there was ANYONE to watch these kids, I'd check myself back into the hospital. Being pregnant is the only thing keeping me from hurting myself again but I still don't feel like I'm living healthy enough for this baby. I'm still in weekly therapy but I gave up my meds when I found out I was pregnant. My house is a mess, the tv is raising my kids, and I cry constantly. My only friend lost her daughter at 30 weeks so she can't understand me right now, she answers every comment I make with "at least you have a baby" which I get but it's left me completely alone. I don't know what to do, even minute to minute. I told my mother I can't do this, and she said I'm doing great, I told my husband and he says "what can I do?" but I have no answers. I just don't know. I keep thinking I should just go to the ER with my cramps, where I'm sure to have a breakdown and maybe someone will notice that I'm not right. But then, who will watch the kids so husband doesn't lose his job? I'm so lost, every day, and I just don't think I can do another 24 weeks let alone manage with three kids. I don't see the light at the end of the tunnel anymore. I'm failing and hating myself for it. I started this post thinking my marriage is a mess, but its me, it's always me.