Talk to Gynecologist on Periods Disturbance

I have always had regular menstrual cycle and never missed my periods since I got them. I got married 7 months back. for first 5 months, I had my periods on my exact due date, but this month and last month, i just had very little spotting on my first day of period, and nothing after that. I took pregnancy strip test as well both months and it came out negative. I want to know why is this happening as I never had any issues in my Cycle till last month.