If you ever sign a buyers agency agreement, you only have an obligation to pay the real estate agent who showed you a home if you should choose to purchase a home that agent showed you using another agent. This usually happens when family members and friends are realtors and the buyer or the other realtor has any respect for the time and efforts the original agent has spent in good faith showing that potential buyer homes and wasting their gas!
If you have just decided not to buy now, no obligation at all under normal circumstances with a standard buyers agency agreement HOWEVER....
There are many agencies out there playing with fees they charge sellers as well as buyers, I have seen buyers sign agreements with buyers that pay in advance for showing "x" amount of homes for a set fee and another amount if they show another amount of homes. I don't know what kind of agreement you signed or what company it was with, you'll have to read that agreement which you should have received a copy of at the time you signed it.
If you're not buying a house, you're not buying a house. There's not a whole heck of a lot to it there.
The only way it would get more involved then that- is if you signed an agreement that provides for a fee whether you purchase a home or not.
Not enough info in your question to answer it. Where are you in the buying process? Do you have a house under contract, or are you still just looking?
If the latter, most every buyer agent who's reputable should let you out of the contract you have with them, however, the contract probably states that any homes they have shown you while the contract was in force, are homes you cannot consider purchasing for some period of time (in the contract), without their being owed a fee.
Since you listed yourself as buyer and seller, are you still going to sell your home? If so, the buyer's agent will probably need some help understanding why it is that you cannot now go buy something.
More info would be helpful to give you better answers.