why, oh why?

I went over to the house of a friend who's about to have her baby. Why did I do it? I was feeling so hopeful yesterday, now I'm back in the ditch of anger and resentment. I don't like being this person. I feel angry that she has her baby (we would have been just weeks apart), angry that I can't be normal around them, angry that being around them makes me feel so crappy, and angry at myself for being a pathetic jealous loser.
It's not just her baby, either. She has all her family around her, and my family is on the opposite coast. She has a house and I'm just renting a tiny little apartment.  I miss my family and I feel so alone. I feel like if miscarriage had happened to her, she would at least have lots and lots of support. 
Why do I feel so physically ill when I see pregnant women? It's beyond jealousy, it's more like rage. It's completely involuntary and very fierce. The only thing I can compare it to is the intensity of seeing a lover who jilted you making out with another girl.
I resent how seeing other people's happiness can somehow steal my peace and my joy.
Somehow, the sadness and the grief of missing my baby is healing, but the resentment I feel towards other people, either for having their babies when I lost mine, or for not understanding, or for leaving me all alone and comfortless at a time when I desperately needed friends--how can anything good come from these damaged relationships? 
The awful thing is, I don't dislike these people, I like them. They (were) my friends. I WANT to like them, I want to be able to hang out with them, but I feel like I have to exclude myself from everything social because I can't deal with my emotions. Especially knowing that IF I still had my baby, we would probably be very close right now. But there's a wall between me and the rest of the world.
Actually, just writing this entry makes me feel the slightest bit better.