Hi.
No one can tell you exactly what’s happening without a physical exam. I can give you some ideas of things to try, but I encourage you to see your gynecologist as well, just in case you have an infection. And by the way, you can’t possibly know that neither of you has an STD without being tested, so please don’t be naïve about this.
Your partner’s diet could be an issue because diet can affect the acidic balance of semen. Your vagina needs a nice alkaline environment for optimum health, and if his semen is too acidic, this can cause irritation.
My guess, however, is that you’re not wet enough, and you’re getting rubbed raw. You should never have p-v sex without being sufficiently aroused. If your partner is thrusting too vigorously, this could cause irritation as well. If you ARE aroused but not producing enough lubrication, then try one of the lubes made for women. I recommend Replens, which is available at drugstores. Be sure to use a lube that is nonperfumed and non-irritating.
If none of the above works, you should see your gynecologist to determine whether you have an infection or other condition. Dr. J
Well he could try changing his diet and also is it possible that you guys are kind off chafing each other? Maybe going hairless, or using more lube would help?