Maria, I don't have a lot of words of wisdom, but I would say he's looking for an excuse to back out of the contract. Have a serious talk with your realtor, if he's breaking the contract over such a thing then you have the option of keeping the earnest money and keeping him to the contract in some states.
Do some investigation, he at least owes you house payments and test costs for the past few months. With a pending contract no one else would make a bid on it. Don't let them walk all over you if you can help it. Folks can be mean for the smallest reason.
Good luck and keep your chin up,
Sharon