I am on adapalene cream for 3 months now and getting under skin cystic acne and my acne was light and was wondering how long will it take to work?

It will not work: Adapalene is not a treatment for cystic acne. Your may need and oral antibiotic or perhaps anti androgens if it is realated to hormones in a female.

Time for a change: It sounds like your acne is getting worse. I doubt that the Adapalene is making it worse, but instead your acne is probably just getting worse on its own. More aggressive treatment is probably needed at this point and i recommend following up with your dermatologist.