Brian is right, if you signed the mortgage, there is no way for you to remove yourself from that obligation without paying it off by selling or boyfriend qualifying for a new mortgage (refinancing). Your best bet is to try to sell the house, even if you can't get what you owe, which would be a "short sale". This can be done, but it will take cooperation from you and your boyfriend. It could save your credit and get you out of the situation. I would be happy to assess your full situation and suggest your best options, just call or email me any time.
Best of luck!