Chronic UTIs!!! Help please!!!

Does anyone else get UTIs basically everytime they have sex? Well, not everytime but a lot. Lately I have had 3 in the last couple months and my ObGyn prescribed me macrobid(did nothing), bactrim(did nothing) and amoxicillin which helped but took the full 10 days to clear up. Now fast forward 3 weeks and another one showed up this morning. I have never felt like I had to pee so bad only to have nothing come out. It was like my bladder was having contractions!!! My doctor ordered urine cultures and said they came back normal, no sign of UTI. I also just recently had a full STD panel run just to be safe and again nothing unusual. Any advice? My period just ended yesterday and my hubby and I had sex, which then I immediately peed afterwards. So I'm at a loss. I drink cranberry juice and use AZO supplements