helpp please

for the past 2 months my period has been super irregular and weird. Ex july i was late by 7 days and in august i was late by 20, but when i was supposed to actually get my period i had brown discharge. i am 17 years old so yes i know how sex and pregnancy works, but my head is getting the best of me. my period is supposed to start tomorrow but i have no symptoms of it coming. i am still a virgin, the closest i came to sex was my boyfriend grinding on me without anything on and me in my underwear (happened end of june) then in august while i was already 20 days late, we did the same thing except he was in underwear but i wasnt. NEITHER TIME DID THEY FINISH ON ME. my period in august was lighter than normal and was medium-bright red. i’m just worried because before these last couple months my period was pretty much regular. is it even possible to be pregnant from this? i’m like 99% sure you can’t but i just need reassurance since i can’t go to my mom for this. thank you