I thought my pimples days were over, but i'm getting them again. is it because i gained weight?

Maybe something else: If a person gains weight and starts having pimples again, the pimples may not be due to the weight gain. There may be a hormonal imbalance that is causing both the weight gain and the acne. Medicine side effects could cause similar symptoms. A doctor can evaluate and do some blood tests to check hormone levels.

Very likely: Nobody understands why, but increased body fat and lack of exercise often increases a woman's androgens, which in turn can cause acne to flare. Think about getting back into a fitness-focused lifestyle, both for your acne, and for your own sake and the sake of those who love you. Best wishes.