Okay so, we’ve wondered this for about a year now.

Basically, I have very unpredictable periods. Some months, I bleed for 19 days, and then some months I don’t bleed at all.

But whenever I’m about to start my period or I’ve started my period, my boyfriend points it out - sometimes before I’ve even started bleeding. He gets CRAZY horny to the point that he can’t focus during his college classes. He can be around me for five seconds in between classes and immediately get an erection, and then be like “you’re about to start your period or you already have,” and neither one of us understand why. But it happens EVERY. SINGLE. TIME. does anyone have an explanation for this?