Your rights remain unchanged whether you leave it or not. If you can't get him to agree to a sale, then it is open to you to apply to the court for an order that the house be sold. In your circumstances, if you are forced to make this application then the court would order a sale and would be likely to order that he pay your costs. I would tell him to go to a solictor (loads give half an hour free legal advice - you should go too - but alone) who will undoubtedly tell him not to be daft and to agree to a sale.
As it's jointly owned the law says that the sales proceeds (after payment of the mortgage, estate agents, etc )will be divided equally. If you did not draw up some sort of legal agreement to say that you would get your extra capital back in the event of a sale then you are stuffed I'm afraid and reliant on his goodwill to get your capital back! In these circumstances, the fact that he is paying the mortgage is neither here nor there. To keep him sweet, you might want to offer to pay half the monthly payment from now until sale' although that would be up to you.
If you leave the house, keep an eye that the mortgage is being paid as you will remain liable on it whether you live there or not.
(I should add that if you were married, things would be different and the court would not neccessarily order a sale whilst there are young kids in the property but that's another story)
If you decide to stay and he gets violent or threatening, you could apply to the court for something called an occuaption order which could get him out and you in so that you can sell it. Hopefully it won't come to that!
Good luck!