You may be allergic to his semen
I'm wondering how aroused you are when you're having penis-vagina sex. If you're having lots of vigorous p-v sex, with hard thrusting and you're not turned on, this may be irritating your delicate tissues. It's obvious that's what your doc thinks. However, I'm also wondering if Depo-Provera might not be involved as well.
It's time to return to your gynecologist and get a thorough work-up. Depo alters your hormonal balance. That, along with not being turned on, vigorous thrusting, etc., may be a recipe for your obvious infection. See your doctor ASAP. Dr. J