I keep constantly getting yeast infections and they do not go away!

I keep constantly getting yeast infections and they do not go away! i tried everything from changing the underwear I wear to something more airy to wearing pants that are more airy to not washing everyday as I used to and nothing helps! I've tried Monistat and it goes away for a week and it comes back!!!! I'm tired of it and I do not know what to do, I'm 16 and I am sexually active with my boyfriend for about 7 months now and he's he only person I've been with. Someone please help!!!!