Marrianne, if you have signed a Buyer-Broker-Agreement you should find the terms under which the agreement can be resolved in there.
However, before you decide to fire your agent, I suggest to have a sit-down, face-to-face conversation first. Let your agent know why you are not satisfied and give your agent a chance to respond.
Sometimes it is just a case of misunderstandings and/or expectations that were not clearly communicated up front.
It is never our goal to have an unhappy client! A conversation may resolve the conflict and if it doesn't then it may be in everybody's interest to terminate the agency relationship mutually. It all depends on where in the process you are at though and whether or not you are already under contract.