I get my period ONLY when I see my bf.

I'm 18F, virgin, on birth control for hormonal reasons. I got my first period at 13 and then literally only 2 times after that. so I didn't get my period for like 4 years. I was put on Nexplanon last year. at first I would bleed every single day. it drove me insane. I've been in nexplanon for a year now and it's not everyday not but definitely every single day that I see my boyfriend. I only see him twice a week, and only on the days that I see him the very moment after I see him I start bleeding. and if I don't see him for a week, I get no period. so basically my period is extremely unpredictable, inconsistent and irregular. is this a me thing? what can I do? 😖 😭