Blimey what a lot of pressure you have on you at the moment!
Hopefully if he seeks some help then that unloads your pressure a little, and maybe he will be encouraged to talk to you about things if he sees someone about this.
You also have to carry on looking out for your unborn baby, and try not to stress too much about when the baby arrives, luckily a woman just goes into caring mode for a baby, so if he isn't so keen on helping in the early days then at least you can do everything you need to for when the baby arrives.
I really feel for you, my first baby I brought up alone even though I had a partner and it was hard and challenging, but also I look back and am pretty proud of myself for doing so.
I really hope he chooses to open up to you. Maybe write him a letter explaining how horribly cut off you feel? And you really want to be a family and want to help understand what he is feeling and help him get through it? xxx