.. upon entry during intercourse. The pain is excruciating. Could this be from the medication or is it me?

Extreme pain from anything requires medical intervention. Did you have a medically diagnosed yeast infection or did you self diagnose?

Is it possible you have an STD?

I am thinking UTI, bladder infection. Either one can be described by some as deep vaginal pain. Monistat would only irritate a UTI.

Tick

Wonder who/why the Monistat? My late husband would see women come in, pick up over-the-counter yeast infection treatments, come back in a week or two with prescriptions for a variety of problems.

Self help is not necessarily a sound idea.