A: The FICO credit scoring formula doesn’t really care why you flaked out; it only cares that you did.
The formula weighs recent behavior more heavily than past behavior, which is both bad and good for you. The bad news is that your scores were almost certainly devastated by the delinquencies, charge-offs and collection accounts you accrued, despite your long history of on-time payments. But if you get your act together and start handling credit responsibly again, you can start to rehabilitate your credit.
Continuing to pay your installment loans on time will help, but you also should think about getting a secured credit card, which gives you a credit line equal to the amount of cash you deposit at the issuing bank. Choose one that converts to a regular card with 12 or 18 months of on-time payments, and use it lightly but regularly. Try not to charge more than 30% of your limit, and pay the balance in full every month. (Perhaps you’ll want to set up automatic payments, as you have with your other bills.)
It may take a few years to recover from your six-month lapse, but it can be done.