My heart goes out to you, N.. I was a single mom and still am. I think the years when my two were little were the hardest. I know how stressful it is worrying all the time and exhausted from working two jobs, then coming home to take care of the kids and try to spend time with them. It does get better--although right now, it does not feel like it will.
I looked up some resources in your area, and I found one that lists places, locations, and phone numbers in your area:
http://hsa.jocogov.org/information/senior_directory/emerg...
Strangely, the directory is a resource listing for seniors, but I am sure they will help you with a little one!
There is some great advice on here by other mothers. WIC is a good program for people who make too much for food stamps. Also, WIC provides immunizations for a reduced rate. It has been a few years, but I think I paid $10 for immunizations. I don't know if there are continuing medical issues for you and/or your daughter but see if you qualify for CHIPS for your daughter. It is for parents that make too much for medicaid but can't afford insurance. Also, ask churches about Angel baskets and ask if you can have your daughter's name put down. They provide clothes (new clothes, not used) and toys for your daughter.
Although it may not feel like it, you are a brave and amazing mother. It is not easy being a single mom. Outside of the stress and exhaustion, there are times you feel helpless and overwhelmed. This sounds like one of those times. You will get through this. My daughter is about to go to High school and my son to Middle school. They do see what I do and have done. I nearly cried when I heard my daughter tell someone that I was her hero. It made it all worth it, and I would do it again (although, I would rather not, but you know what I mean). Send me a message, and I will see what I can do to help. Know that you are not alone.