Brown spotting for 5 days

I assume it is my period. But it is very unusual for me to have a light period. It was all brown and never filled a panty liner. Also my rhr never dipped like it normally does during my period. I took a pregnancy test when I started spotting and it was negative. I'm on clomid. 50 mg. I didnt start my next round because my husband and I agreed to take the holidays off. I need some insights. I've read people experience this and are pregnant. Also have read that clomid is the culprit. I just dont want to spend money on a pregnancy test for no reason