Sorry you're going through this. I can't offer any advice but did just want to say that my DH and I generally have a VERY good relationship but I have found being pregnant very trying on this. I'm so hormonal and DH just doesn't know how to deal with it a lot of the time. I would suggest that you don't rush into any big decisions while you're still pregnant as I think it is just a difficult time for both people. Hopefully it will settle down when LO comes and hormones all go back to normal. xx
Just to let you know, the hormones are going to be much worse when LO's here, the stress level will go way up as you'll be sleep deprived and having to deal with a screaming baby, if you're like most couple, you'll feel resentful towards each other over sleep and household and baby chores. My relationship was the best during pregnancy because it was planned, now we sometimes barely speak to each other for a week. It's best to make a deal with each other that you'll stick it out for the first year at least.
OP, have you tried talking to your partner about why he's acting this way? I don't know in what way you feel your relationship is unhealthy so can't offer much, but if it's just from stress, talking could help.