HELP!!!

So I’m today I’m 20 days late and had my last period August 12-16 and had unprotected sex August 19th and he said he cummed in me a little (tmi sorry🙃) i was supposed to start the 12th of September I’ve had mild cramps and today I felt like my period was FINALLY here and I had brown blood In my underwear but when I wiped it was red so I put a tampon in and 2 hours later I took it out to find out I had only a small amount of brown, and left it out with only a liner on, so here it is late tonight with no more blood, could I be pregnant