Period or pregnant ?

This started the day I was suppose to start my period so I didn’t think anything by it for the first day, but my whole period this month was so light. Like spotting and it was mostly dark brown. Some days it would be red but mostly brown and so light. I’ve recently missed a couple of my birth control pills.. has anyone experienced this before? Could it be my period and it just be off track because I missed pills or could this mean pregnancy? I took a test two days ago and it said negative.