Skipped period -negative test

I have never missed a period till this month. Last month it was only 3 days long and kinda dark brown but not heavy at all. I have taken preg test blue and pink and all negative. I had blood work last year and test came back normal. I am TTC and its been about a year. Any advice or anyone been in my shoes? Is a skipper period normal? Could I be preg or should I make a doctors appointment.