You need to get out of there ASAP. It is NOT your fault that he is hitting you. It sounds like since you allowed it to happen it may have changed his boundaries with you. You need to leave, maybe tell him if he gets help and completes a program you would consider dating him again, if and only then. And if he ever hits you again you'll be out of his life forever. Easier said then done, but do it, you'll never regret leaving because it will either change him and free you, you'll always regret staying. Don't ever let anyone abuse you again ever, have more respect for yourself.