You made a comment about never being engaged. If you don't mind me asking is this a sarcastic remark or something you are comfortable with?
I do agree with everyone that says you are paying to much to live there. You are essentially paying for a house you may never get any benefit out of paying for. I could understand if you both rented a home or apartment. Neither one of you will ever own it and that seems fair to split. But if he already owns it, why should you pay so much? I think it would be fair if he took care of the mortgage and you took care of everything else. Like lights, cable, heat, etc. my friend recently just moved in with her SO and the same thing happened to her. He has a room mate so somebody is already paying half the mortgage and he wanted her to pay the other half! So he really wanted to live in his own house for free. I would sit down and have a talk with him or evaluate what you feel comfortable paying. Good luck.