The seller of a house is unlikely to share with you the other offer as that would be revealing information that can hurt in their negotiations. I have once told a 2nd agent the name of the agent that brought forward the offer, but otherwise I would not advise my seller client to share anything else for information. REALTORS are bound by the code of ethics, which prohibits lying about the existence of another offer, though I am not saying that they have never lied... it happens in every profession.
If you do not trust your agent you should confront them and see if you can build reassurance. If you cannot, then you should speak to their broker.... more