You really need to consult an attorney. It sounds like you are dissatisfied with the way your transaction happened and without reviewing all the documents and knowing NY law, we are not in the best position to advise you. Your likely recourse would be legal anyway, so you might as well gather your documents and set an appointment with an attorney as soon as possible. Sorry about your situation.
Of course, the agent should have disclosed it in writing...what I'm wondering is if his negligence in doing so...would have made a material difference to your decision to buy the home.
Think about it...
All the best.
Mitch Lubinsky, Broker - Realtor, Mortgage Banker
Assuming that you are purchasing a property in Burlingame California, the first form that your agent would of had you sign was the Agency Disclosure form that explains both Single and Dual Agency between your Realtor, yourself and the seller. At that time your agent would have told you that he would be representing both yourself and the seller.
If you have any concerns that you were not represented properly during the negotiations in the purchase of the property and you already have a Ratified Purchase Contract I would have a conversation with the Broker that your agent works for. If you don't receive satisfaction at that point than the next step would be to get legal counsel.
1 question that I have is at the very top of page 1 of the purchase contract where it mentions who the Listing Agent and the Selling Agent represents(Buyer, Seller or Both), were the boxes checked correctly before you signed them?