Am I pregnant?

Yesterday my boyfriend and I had sex and my period was due yesterday. Afterwards I just kept spotting and I thought it was my period but it’s still light. Usually the next day it gets heavier but it hasn’t. Btw I’m on birth control and I haven’t missed a pill. Should I be worried and test? I tested yesterday the day my period was suppose to be due and it was negative. I’m just worried because my period is soooo light. Btw I don’t think I’m pregnant from yesterday’s sex I think if I am pregnant I conceived on September 23rd or 35th.