body stress!! please help

so listen. my period is 12 days late. i’ve been on birth control but i stopped taking it a while ago because it made me way too moody. the point is, my periods aren’t that regular since then. i just moved back up to college and school has really hit me hard early this year and i was wondering how much stress/ a change in environment can effect your period! i’ve actually taken a pregnancy test that came out positive and showed positive immediately when i peed on it!! i’m afraid that i’m not actually preg and just about to start my period but have 2 extra tests to take just in case. am i too stressed? is there a way to help start my period if i’m actually not pregnant?