No period while on pill, heavy workouts

I workout hard, cardio, lifting, sprints, everyday or 5 out of 7 days of the week and if I’m not I’m playing in games/ tournaments. I’ve started the pill recently and I am not getting my period at all, I used to before I went on the pill. How do I get my period back while on the pill or how do I know I’m not pregnant? Thanks

Also I’m 5’1 and weigh 118 along with following a vegetarian diet with supplements!