If the offer is accepted and the contract is signed by the seller, then it's a different story. You would have to review your position with your realtor and/or attorney to see under what conditions you could cancel the contract, and see how it would effect it would have on getting your money returned.
I agree with Mr. DIna below in saying that it's never a good idea to submit multiple offers on multiple homes simultaneously, as you may very well wind up losing earnest money if multiple sellers accept your offers (that is, unless you want to buy several homes at once).
Check the terms of your original offer to see if the seller had a certain amount of time to respond before the offer expired, have your agent pursue the seller's agent to see what, if anything, the sellers are doing about the offers, and, as always, consult a real estate attorney on the matter.
Hope this helps! Good luck!
Putting in multiple offers may mean you are going to be buying multiple homes!!! I would NEVER allow a client put in an offer on more than one property at a time.
If you want to withdraw your offer, put it in writing and instruct your agent to get it to the sellers immediately. Once it is withdrawn and you have your EO back, then proceed on to the next property.
DO NOT be in a hurry to buy a home. Always buyer beware (caveat emptor).