Pregnant or period?

I started my period yesterday but I noticed how light my flow is, lighter than usual. I don't think if it has to do with the pill but it hasn't been this light unless I'm on my last 2 days of my period. I don't know if it has to do with how stressful I've been the past 2 weeks or that I took my pill 40 minutes late then had unprotected sex or how I didn't take my last active pill before taking the sugar pills. Please help!