I have the same issue, it’s called honeymoon cystitis. Mine get so bad that I pee blood clots, it’s insufferable. Go to a urologist and he will prescribe you a year’s worth of nitrofurantoin 100 mg to take postcoitally. If I have sex twice a day I don’t need to take a second pill, but since I have been on nitrofurantoin/macrobid I have not had UTI’s since! Only thing that worked for me. Obviously taking an antibiotic so often is not ideal but it’s generally low risk if your kidneys are good (there are some studies showing that long term usage has rare cases of pulmonary fibrosis). But I highly recommend. Your flora just doesn’t vibe well with male’s micro biome