preg??

ok i don't even know where to start but lately i haven't been taking my birth control and i've had sex and it was during my fertile window and i'm just really scared and i've been taking pregnancy tests and it wouldn't show up yet but i'm not supported to get my period until the 27th and now i'm bleeding and it's really heavy like i bled thru my sweatpants last night and that never happens. is this a miscarriage or what is happening?