Being a Single Mom

I am a single mom. I have a son, 2 1/2 years and a daughter, almost two months. She's still not sleeping through the night yet and some nights can get pretty long. We're living with my parents and although she has her own crib, my son doesn't have his own bed so we share a bed in my room. My parents have been so helpful since I've lost my job, I wouldn't know how to begin to repay them for the last couple months. I'm still struggling to look for a job now and once I do, my mom will probably be the caregiver for both my children. My son won't go to sleep until I do and sometimes, depending on when my daughter is eating, it can be as late as two o'clock in the morning.
Sometimes it gets hard, and I feel frustrated that I'm the only one giving up sleep and taking care of both of them during the day. I also hate that their father never calls to see how they're doing or asks when he'll be able to see them again. When he does see them, he doesn't like to change the pampers or feed them. It's usually his mom or sister that helps out when they visit. It frustrates me mostly for my children, because they'll never see him as a father figure unless he learns to grow up. Sure his name will be "Daddy" but all the responsibilities and sacrifices that come along with that title mean nothing to him, it seems. God forbid I ask him to change a pamper or feed the baby or my son. He always asks why I can't do it, or passes the job off to his mom. If it was the other way around and for some reason he had custody, and I was the one who only got to see them once a week or once every couple weeks I would die to be able to change every diaper I could and be able to hold the baby to feed her. I just don't understand. Sometimes I think, "Well, it's his loss." But really, its not. The kids are the one who are losing a father figure. They're losing that relationship that I think everyone should have. I hope one day he wakes up, grows up and realizes what he's missed all this time. I hope....but that's all I can do for now.