I'm on day 12 of my first Whole30 and my period showed up two full days early. I'm on bcp so usually I can predict the start almost to the hour, so this was definitely a surprise. Hoping this doesn't mean it'll be longer...since I've been on bcp it's been 3 days, very little cramping or back pain, so I'd like to keep that going! It'll be a small price to pay, though--I usually get a migraine on day one, and I haven't had even a flicker of a headache so far.