J.C.
What you are smelling is mildew. Do you have carpet? If so, rip it up. Have pros (or a handy husband) seal the entire basement. You need to keep the wetness out. Then, either tile or put down a "floating floor."
The well and septic have nothing to do with the fact that you likely have a "wet basement". Google that for more info. And good luck.
And do try some Damp Rid like Pool Mama suggested. It should help a little.