One thing I have mentioned here a lot, and I will do it again now. When you have a yeast infection, both you and your partner need to be treated for it, even if he has no symptoms. Otherwise you just keep on giving it back and forth to each other. What I would do is I would buy the yeast medication cream you can buy over the counter, and then I would insert it into my vagina as directed and have sex so both of you get basted with it. i mean it's not gross or anything. just don't have oral sex for a while. Of course if he uses a condom, then that may invalidate what I just said. Could you maybe try a different type of birth control. i had similar problems like you in my twenties, and those yeast infections i remember were the worst. I didn't have cysitis though. when I got a few years older, i still had the infections once in a while but never as badly as the first time.
The other thing I say in this contest is this: do not use ordinary soap for those intimate areas. you wouldn't believe how many women and also men are allergic to soap down there. (It's OK to use it on the rest of your body) Since I don't know off hand something to recommend, I know that EVE makes a product that comes in a bottle that looks like shampoo, and it will work great. Try it and let me know if it helps.
and i just wanted to add that i drink plenty of water and cranberry juice everyday, i eat yogurt everyday, i pee both before and after sex, wear only cotton underwear, use perfume free laundry detergent and sensitive skin soap. what am i doing wrong??!!