Lots of sex will make your vaginal wet nearly all the time, which increases the likelyhood you'll get a UTI, even if you clean up afterwards. I have the same issue. Talk to your doctor about prescribing you an antibiotic. I'm just as crazy about my boyfriend and after I came in 4 times in a month, my OB/GYN just prescribed me a 90-pill supply, and to take one or two doses after alot of sex, to ward off possible infections.
Go with a KY lube, as the mouth has alot of bacteria in it. If you have sensitive skin go with something with no fragrence or tingling or warming.
Also the kind of infection will tell you what you can be doing. If its an E. Coli infection, it's the too much sex or improper wiping techniques (front to back). E. Coli naturally grows in your intestines, so if you're having anal sex, make sure he washes himself or uses a baby wipe before switching to vaginal sex. Or being wet all the time during sex can cause an E. Coli infection too.