Weird and random acne problems

[Zzeuse]

I usually have clean, healthy and acneless skin on my face. But, for some reason I get the most random breakouts on my entire face from time to time. My diet is healthy and almost always keeps my skin clear, I can eat the same things for over a month and have a normal face until one random week I get a crazy breakout, covering my face in at least a dozen pimples and making me look disgusting. If I do eat something unhealthy for some reason I usually just get a few pimples and they go away quick. I have no idea what causes these and id like some help