When will my skin clear?

I had completely clear skin all my life up until this year. A couple of months ago I started breaking out. I mean I have large cystic acne in places I've never had a pimple ever. The only thing that's changed in my life is that I was drinking a whey protein shake everyday since last august. I quit drinking it 2 weeks ago and I'm not sure if my skin improving. I have a lot of scars now, but still I have pimples and tiny bumps around my skin. Will my skin improve? How long will it take?

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