Credit score....I don't understand how it is so low.?

I just ordered my credit report and score from equifax. My credit score is only 555. I have been doing very good paying ALL of my bills on time for at least the last year. On my report, under negative accounts, there are three things listed :$408 cable bill, $146 cable bills (reported 2006) and a finance company that says paid 31-60 under account status (with zero balance). Under revolving account, I have 1 credit card with $200 limit and $170 balance. I know this is high, but I just opened the card in December and haven't made the paymeny yet. Under installment accounts, I have 7 accounts.....three of which have zero balances (they were loans I had but have been paid off). There other four are 2 car loans and 2 personal loans. Do I have too much credit? I really want to buy a house in the next 2-3 years and thought I was heading in the right direction until I saw my credit score. What are the best ways to raise it? I already pay all my bills on time.