Information from an online provider rarely is more reliable than that from providers who actually have examined someone. Since 2 doctors say it isn't herpes, it isn't herpes. And it doesn't sound like it to me either; herpes doesn't cause the sort of inflammation you describe in the folds of the groin. Sounds like typical tinea cruris (jock itch). Follow up with one or the other of your doctors if it doesn't clear up on Lamisil.
Best wishes-- HHH, MD