Advice ? (Possible pregnancy)

Okay so I’ve been seeing this guy and we were having sex then we hadn’t had sex for a while and I got my period. A few days after my period ended (which would have been the first day of my fertile window, btw I’m on birth control) we had unprotected sex and I had been drinking a few hour prior. He never ejaculated at any point during the sex (strange I know). Now it’s three weeks later and my period is 4 days late but I have been having very light brown spotting when I wipe or left behind in my underwear. I plan on taking a test in the morning but I’m having a lot of stress and anxiety. Any advice? Could this really be pregnancy ?