I hope you keep venting. Lots of people here who understand.
You do need all the support you can get, I would really, really encourage you to try al-anon or another support group. Right now it is probably the last thing you want to do, drag yourself to a meeting with a bunch of strangers - I understand.
Thing with Al-Anon is, you don't have to speak if you don't want to, they will totally understand that, no questions asked. It does give you the opportunity to meet people and hear their concerns and how they cope and usually there is a list of people you can all if you just want to talk.
It might be a huge relief to have that kind of support. Many will have been where you are and they will tell you how they coped and the tools they used.
Anyway, that's just one avenue to use to make yourself feel supported and understood.
And of course there is always SR,
I can see it's taking a huge toll on you and yes, this should be a really happy time for you. You mention you are almost at the point where you don't want to do it anymore, well you know, you don't have to. You aren't actually responsible for him. All your love and kindness it wonderful but he is still an addict. You also can't throw yourself under the bus for him, especially not now that you will have a child to look after. That, as I'm sure you know, will have to be your number one priority and that also means looking after yourself. You deserve to be happy too you know.