I had really bad cystic acne so I went on accutane and my skin cleared up, but now it's coming back. Is this normal?

My face has always been acne prone and I used to have really bad cystic acne. I did a 7 month course of accutane and my skin completely cleared and I was so happy - for about 3 months. Now its coming back, not as bad as before but bad enough that I had to go back to the doctor. I'm now using a topical treatment and I've gone on birth control (I'm 18). I thought I would have stayed clear for at least a year. Will this be enough to help me get clear again or does this mean I'll need another round?

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