What Causes Light Spotting And Brown Discharge During Periods?

I had a tiny drop of blood and brown discharge yesterday and today, I have a bit of cramping now and again not painful I am due my period, I had brown spotting for a day or two a week ago. I had a blood test done last week that came back negative for hcg I done a urine test today as though maybe the blood test was too early and that to came back negative. My period is usually regular and nothing like this, I normally start with brown discharge which gets heavier and more red, not sure what is happening and what to do, thank you