Sodevestated,
I wish I could reach through this screen and give you a hug. I'm so, so sorry for what you're going through. My friend is going through a very similar situation and your situations sound so alike, it's heartbreaking. I'm not sure if you've looked into it yet, but she was able to collect social security survivors benefits for her boys. I'm not sure how it all works, but please look into it for yourself and your little guy.
My son is now 21 years old, however, his father left when I was 5 months pregnant. I went through my pregnancy and the birth of my son alone. My situation doesn't compare to yours, but I felt the exact same way seeing happy pregnant couples. I couldn't understand why I was given such a raw deal and it hurt like hell. I don't think I hurt as much for myself as I did for my unborn son. He didn't deserve it. The financial part was devestating as well. My electricity was turned off while I was in the hospital and I had to have my mom pay it to have it turned back on. I never, ever thought I would pull out of it. But, I did. And I raised my son, alone. There is no way I'll sit here and tell you that it was easy because it wasn't. I had to put my college career on hold and work 2 jobs, but thinking back on the days when it was just him and I, they were some of the happiest days of my life. And some of the saddest, too.
The silver lining is that my son turned into an amazing young man. He works hard, he has a great career, he's continuing his education, and he's probably one of the kindest, most compassionate 21 year olds I know. He respects women, he's smart, he has a great head on his shoulders, and he's honestly one of my best friends and biggest cheerleaders. And after the hurt, pain, and hard work, I can say that although my situation was awful in the beginning, it got much better and, I raised a damn good kid! THAT is the most priceless gift in the world to a mom.
The pain you feel when you see a happily pregnant couple will subside. The hurt you feel when you see couples with their children will ease. You still have A LOT of life ahead of you and you never know what tomorrow will bring.
I wish you so much strength and happiness. This will get better.