Suspected yeast infection. Sexually active. 2nd month off birth control. Never had one. Red, itchy, inflamed, white substance at vaginal opening, no smell. Will monistat be as effective as a prescription antifungal? Is a doctor visit worth it?

Maybe. Many women self treat what they think is a yeast infection with Monistat & find it effective. I memory serves me correctly it was a prescription med many years ago but it's safety profile allowed it to be moved to OTC. You might try this initially & seek an appointment and or prescribed meds if it does not respond.