Hi I Had Intercourse 4 Weeks Ago. I Came On

Hi
I had intercourse 4 weeks ago. I came on my period last tuesday & came off yesterday. Usually my periods last 5 days, regular & are extremely heavy with crippling pains which I have medication for. However this time round.. it started off with a brown/pink spotting discharge, I only had one heavy flow day before it lightened again. I had absolutely no pain whatsoever. extremely tired. Needing to pee constantly. I did do a test today... negative. Do I need to retest or could this be something different