K.S.
Wow, S.. I can feel your stress and upset just by reading your post. It's overwhelming what you are going through. I'm so sorry. The first thing that comes to mind is that this is a horrible time to make any big decisions, so please don't make any big moves for a while, at least until a few months after the baby is born (congrats, btw).
It sounds like you are going into the medical field, so you are familiar with triage. This is what you need to do for yourself right now. Decide what the issues are that you are facing and sort of 'rank' them.
If household help tops the list, then start there. Time with son? Money? Sex? All issues, but where do they rank? In between, you are surely grieving your losses and trying to focus on school. And you feel alone in this.
I don't like when people turn things like this against you and point out that you play a part in this marriage as well. This just piles on and is not helpful right now. However, giving your husband the benefit of the doubt I will gently suggest that he may be overwhelmed as well. He probably feels the burden of providing for a growing family and may be unsure of how to deal with your stress and emotions right now, and feels like he can't do anything right. Not excusing anything he's done, you are obviously unhappy, but just asking you to step back and at least glance over to his side for a second. This just lends some perspective.
So back to triage. If housework is the thing that might lighten the load for you right now, start there. Tell hubby there is a lot going on for you both right now, but for now you would like to start with figuring out to run the household better. Ask him if he has ideas. (even if he is a huge slob and completely wrong, telling him this and demanding help won't work, try to include him in the process). Perhaps suggest that you guys make a list of the things to do and decide who will do what. This puts some ownership on him, and also lets you express that you need help with the heavy lifting, etc before it's in the moment. Keep that list handy and where he can see it.
Money, sex, etc.... try as best as possible to put these on the back burner. You can't solve every problem all at once.
Then start letting him know you guys perhaps need some counseling or a marriage retreat. Start looking these up and making arrangements to go once the baby is a few months old (give those hormones some time to settle!). Ask if he would like to help find someone or someplace. If you need to start saving money for this, do it.
If, after everything, you need to leave- fine. But now is not the time to make that decision. You need to know that you didn't try to leave in the middle of a tornado and without trying everything possible.
And, I'm sorry, but if anyone suggests reading The Care and Feeding of Husbands, please don't bother. Nothing like reading how this is all your fault to make things better. :-) (sorry, this is my pet peeve!!).
Good luck and God Bless.