Weird brown discharge after sex... am I pregnant.

My bf and I had Sex 3 days ago for the first time. We did not use a condom bc I am on the pill. He pulled out. But since having sex, I have been having brown discharge. I’m not sure what this means. Does it mean I’m pregnant? I know the pill isn’t always 100% preventative.

It’s been going on for three days now. It has never happened before.

Thanks!