Help! cystitis or something else?

So i have chronic cystitis, i’ve had it since i was little and i’m not sure why, i’ve had this bout of cystitis for about a week now, i went to the doctors and they gave me anti biotics to clear it up. it went away but now it’s come back all of a sudden, and there’s stringy blood when i wipe (i had this last time). i am in a good relationship and i am kind of sexually active but it doesn’t happen often. im stuck on what to do anymore because it’s getting close to my gcses and i can’t keep missing school, do i go back to the doctors or just drink water religiously and see if it goes away?