Frequent UTIs

Alexis
I get UTI s ALL THE TIME!!! I hate them and they are always so extremely painful!! I pee after sex, wipe from front to back, drink lots of water, change my underwear, don't wear pants that are too tight, take cranberry pills.. What am I doing wrong?! I'm sick of getting these and my boyfriend is sick of dealing with me when I have them (and I don't blame him lol) can someone help me??? 
P. S. I went to the doctor and they tested me for STDs that could be causing frequent UTIs and I did not have anything. It was all completely healthy out there 🙃