How long should I wait to re-apply for a credit card?

Ok Kind of a long story. Im 22 and went to buy a new car, the dealership said I would need a co-signer due to the fact that I have no credit. I don't own a credit card and I am currently not financing anything. He suggested that I open a small card and start building my credit. Well I applied with capital one and they denied me. I was curious why so I got a copy of my credit report and low and behold I was $4000 in debt. Apparantly when I was 17 I was on my fathers insurance. I was sick at the time and seeing doctors. Well I hit 18 and my father never bothered to tell me that insurance stopped paying on me because I wasn't in school. He never told me about it and now I had to deal with the debt. Well in the meantime I applied with citibank and Target and they both denied me as well. Well I paid off the debt and re applied with Citibank and now they're denying me due to, to many credit card inquiries. I even tried getting a loan from the bank and paying it back just to build a credit history, and they stated they were only giving out $10,000 and up due to the economy. I have no money issues so I don't need the credit card speech lol. I live in a home thats paid for by my boyfriend and my car is paid off as well. I need to build my credit not only for a new car but a home mortgage down the road. I just need some insight as to when I should re-apply or any other options that I may have?! Please help im going insane!