How come i get cystitis every time i have sex?

Bad luck: This can happen to women. Mostly is a result of the fact that women have short distance for bacteria to travel to get from the external opening of the bladder to the inside of the bladder, and intercourse generally brings bacteria into closer proximity to the urethra. It's why women should always go urinate after intercourse, to try to 'flush' out the bacteria and prevent infx. Cranberry pills can.