As it is a joint mortgage you do not need to worry "where you stand" as you own half the house and he cannot do anything about that (even though he is paying the mortgage, you are still contributing by paying for everything else).
You will almost certainly find the value of your house is less than it was when you bought it 2 years ago, it is also a very bad time to sell.
I guess you have 4 choices:
1) Stay in the house together, but not as a partnership, almost as two "friends" sharing the same house, until the housing market picks up. This may be difficult bearing in mind you were in a relationship.
2) He tries to raise the money to buy you out
3) You try to raise the money to buy him out
4) If neither of you can afford to buy the other one out then sell the house and split whatever is left after paying off the mortgage.
whatever you do, dont just move out and give up your half. You are entitled to half the house (assuming there is anything left after you pay off the mortgage).