Dear Southern Lady,
I completely understand your position. Please allow me a few suggestions. First, talk to your agent, there is a chance that with his/her broker's permission, she would be able adjust her commission to to enable the sale.
Depending on how close you are to what you need to pay off your mortgage, you might try to negotiate that with the potential buyers and be upfront about it, however, please note that the bank providing the financing for the potential buyer will ultimately decide what you home is worth and what they are willing to finance.
Above all, you need to find out what your "protected buyer" time frame is and that is dictated by your state. If they viewed your home during the time that your agent had the listing you could potentially end up owing a commission to your agent.
I'm not sure of you particular circumstances, but you may want to inquire about a loan modification. If you must sell for less than you owe, then you might want to consider a short sale.
If you still have your home listed with an agent, he or she should be able to help you with further information on how to go about doing that.
Hope this helps.