Should I be worried?

So yesterday I had unprotected sex with my boyfriend. Before we had sex we were already tested and we both came back negative. I am on birth control I started back in May of this year. Today I noticed brown blood in my underwear. I doubt I’m pregnant because I don’t think I wouldn’t get symptoms this early because we just had sex yesterday. Yesterday I was sore down there and it was uncomfortable to sit but it wasn’t unbearable pain like I couldn’t sit. I should start my period next week. Per Glow my chance of pregnancy is 3%. He did nut inside of me too. Should I just not worry about it since we had rough sex? Or should I?