Your question is a little vague. Did you give a down payment check and has it been cashed? Usually if that is the case and you have signed or are signing a contract, you would have an attorney representing you who should be advising you and answering this question for you.
Normally, the seller would sign the contract after you and deposit the down payment check at which point in time the seller's attorney would forward a fully executed contract back to your attorney. Until this happens you are not in contract.
Once you are in contract the seller is legally obligated to you and there is no point for the seller to continue showing the house due to this fact. It would just be a waste of time. Theoretically the seller can still show the house if he or she wants to back themselves up just in case the buyer does not close for some reason, but if the seller felt there was a chance that the deal would not close, they probably would have not taken the offer in the first place.
With regard to the seller not being willing to give you a copy of the contract until you close, that is crazy and does not make any sense to me unless there is some weird circumstance that you have not stated in your question.
If I can be of further assistance, please let me know.
Mitchell S. Feldman
Associate Broker/Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665