pregnancy

I got my period october 6th , which lasted until october 11th, on october 20th i went to the bathroom and noticed a light brown discharge, now i’ve heard about old blood from your last period, i’ve have my period for four year and i never encountered "old blood" this discharge lasted for 1 day , i had to wear a liner, im suppose to start within 2-3 days so all i can do is wait, can anyone whos experienced this before tell me what this is, i’ve ask other people and one of my friends mom said i might be pregnant i bought a test but it said i should wait untill the first day of my missed period, but its just that im so confused and i just need a reasonable answer from someone.. thank you <3