how does acne form

My mom keeps saying that its because I’m dirty and that I don’t wash my face good. I used a cleanser and scrub everyday. I used to have acne long time ago too but then I started using proactive and it got better. My skin was really good and I thought I didn’t have to use Proctiv anymore. Like 2-3 days after I started seeing my acne. I didn’t want use Proactive again cus I heard it can damage your skin and it has a chemical in it that makes your skin addicted to it. So what should i do?