penis irritation

My boyfriend for the last year has had the following problem:
2 days after we have sex, intercourse and oral, he says it feels like a rat is gnawing on the end of his penis. This lasts several weeks and slowly seems to subside but never feels normal. He has no sores, no discharge but it is worse after his first urination of the day. It is not sore to pee but is sore afterward. We have used condoms for the last 2 times but it is still happening, wondering if it is from the oral i am giving him. I have been tested for every std and all negative. This is beginning to ruin our relationship as he is afraid to have sex with me yet to stubborn to go to a doctor. He thinks he is allergic to me. The only other complication he has had, is one time 6 months ago his penis flaked off dry skin but that has not happened again. He says it feels like the inside of his penis is itchy and his urethra opening. He has never had this issue in any of his past relationships and in fact when we split up for awhile, he had sex with another woman and this did not happen. Help at a loss