How to fix my credit? Past collections?

I am young, 21 years old working right now. 2 years ago I was taken to the hospital and ended up having a blockage in my intestines requiring a 2 day stay in the hospital. I did not have insurance at the time and was in my freshmen year of school (19 years old). I got slammed with all kinds of bills ($10000 doctor bill, assorted hospital bills for xray, labs, ect for another 1000 or so). Back then I was young and stupid and didn't really know the financial impact it would have on me. My dad who was paying for me back then through school and stuff I guess sort of let them go and they were attached to my credit report as collections. Until now I really didn't think it mattered but I've grown and realized the importance of it. I would like to begin to start taking care of it. My credit score is low (low 500's). I am currently working full time. I have been doing research about paying off the collections and read that unless the company would be willing to delete the entry (most wont already asked) then it will end up hurting me more. Spare me the spew about how I should have done this and that, I realize that. I'm looking for honest advise on what to do. I really don't know who to contact. I want to make the best decision to raise my score. I can pay off a good portion of it, but like I said I read the older the credit the less impact it has. Another problem is getting a credit card or something to help increase my credit worthiness is hard. No one is going to issue me a credit card with a CS in the low 500's I even got denied a secured card from wells fargo (who I have heard have high standards on those). I'm just looking for some honest advise.