First call a Title company for your local area and explain your situation. They should help you or point you in the right direction. You can Google this for your area. Then you will need to contact a real estate attorney and explain the situation to them. Between the Title company and lawyer, you should be on the right path.
One major question that will be asked: Do you have the cash to pay the $15,000. in back taxes? Once the title transfers to you, don't expect your boyfriend to pay anything towards the back taxes or maintenance. Everything will be your responsibility.
As an older adult, I do have some advice for you. Since he owns this house, his credit has suffered with the bankruptcy and back taxes. Don't let your credit suffer. If you can get the title or deed to transfer to your name, the best option is to sell the home and walk away with whatever profit you can get. You spent money maintaining the home, so hopefully it can sell at a fair price - not a foreclosed price. If you do sell the home, then find a home that is AFFORDABLE where you won't need to claim bankruptcy. I would also consider dumping your boyfriend. There are men out there with better finances.