SOS light period 6 months into BCP

Sarah

I have been on Sprintec (birth control pill) for 6 months. My period usually starts on Wednesday of the sugar pill week. This month my period started on Wednesday (as usual) but was much lighter (like spotting). I have taken 4 pregnancy tests all negative. Is it common to have a lighter period 6 months into the pill? I normally have a heavy flow. Thanks!