Plan B spotting or Pregnant?

So my bf recently ejaculated inside of me (for the first time) on Sept 9. at like 2am. I took the plan b pill on Sept. 9 at around 9pm so about 19 hours later. 8 days later on the 17th I started spotting. It was very light and it was a brown color then turned pinkish brown. Then on the 18th, it turned red and TMI, a small clot came out. Then yesterday on the 19th, I was still spotting for most of the day but it stopped at night. Could I possibly be pregnant or do you think it was spotting from taking the plan b? Also, I'm around 200 pounds, sometimes 203 pounds so plan b may be less effective or ineffective in me so I'm stressing 😅😅😅