That's usually how pretty much any medication works.
Take anti-anxiety meds for an example. I know a person ((LOL, and no, it's not me). , who several times has taken herself off her meds without doctor's okay and help. She's fine for a few months ... maybe even 6. Then all the sudden, her anxiety hits hard and she litarally freaks out. Gets violent and tries to hurt herself and others. But she thinks she's fine and doing better, because she feels much better off the medication.
I've seen it lots of times. With different people.
Work closely with your doctor. Demand a different treatment if you feel the one your currently on isn't working. Maybe your dosed to low or to high or maybe the medication itself just isn't the right one.
One of my kids has problems she needs medication for. She's seven, first started meds when she was 5 1/2 - 6 ... she's been on six different meds already, countless different doses and we still haven't found the one that's completely right for her.