Stop looking at online sources. It will only drive you crazy. The more you read about STD's the more symptoms you seem to magically acquire. Focus on your health both physically & mentally & find a doctor that you trust 150%.
From your description, herpes does not sound like a possibility. As you suggest, tinea cruris (jock itch) sounds likely. Another option is erythrasma, a bacterial infection that typically occurs in the folds of the thigh and groin; it does not respond to Nizoral or other antifungal medications. If you or your doctor have any doubt, ask for referral to a dermatologist. But don't worry about herpes; it doesn't cause the sort of rash you describe. I truly don't think you need to worry about it.
Good luck-- HHH, MD