Im 14 and I've had acne on and off since I was 12

Sometimes I would have almost no acne at ALL

and other times like right now It's mild..

What makes my acne break out all of a sudden? Just at random times..like one month I'd have normal teenage acne then another I'd break out really bad?

What factors contribute to this? and If food is one of them what are some foods I can eat to make my skin healthy??

please and thank you!