Although it may sound very usual - but trust is THE most important thing and at times I also think that it cant be something you can find, loose and find again.
If I were you I would seriously reconsider everything happening with your life at the moment. Especially the fact if you can overcome the trust issue and stay together and if so, than for how long?
Each of us do our bit of mistakes, they are not always bad (infact they are good for they make you a better and experienced person) but its REALLY important that we end up with someone who don't have a tendency to blow those mistakes out of proportion . applies to both the partners in a relationship (remember the old-ladies tale, we are not perfect but we can tolerate each other like no one else can). name-calling, blame exchanging or negative reciprocation or vindications don't really have a space in an intimate relationship.
Also you cant change people, you have to love them the way they are, and if there is a problem with them which is as fundamental as 'trust issues', I would say - seriously reconsider your approach and decision. Is there a better way you can deal with things (including seeking a professional therapy session for couples), how important is this relationship to you personally (your child would be happy with what you are happy) and when thinking of importance of the relationship think of not the time right now (because you are pregnant you need support - everyone does) but in a long run (after the baby is there and grown-up enough to understand whats going on in the house).
There is a lot that you need to re-evaluate in your situation, do it one by one. Also, that task of noting the good things and bad things about your partner is really helpful, note them down and if the good things are more in number than bad things, probably you want to work this relationship out genuinely. And where there is a will there is a way.
About the stress- of course its not healthy for the baby development, but those tiny ones can deal with all those things that you yourself can deal with. So if you cope well the baby would be fine too (except in circumstances where there is physical abuse, than I would say completely get away from the abuser!)
take care and wishing you all luck