My Husband Has Been Complaining That He Feels Burning When

my husband has been complaining that he feels burning when he pees after having sex with me. it only lasts for about 3 days and then no more burning. we've only had sex about 4 times in the last 3 months and it has happened after each time. i do not have any other sexual partners and my last std tests were all negative. i do not have any burning with urination. oh, and he did not ejaculate the last time we had sex and he still got the burning. any ideas would be appreciated. thank you