Menstruation is less than usual

Hey ladies, so I got my period yesterday and I noticed when it hits it was just a drop of blood literally nothing. I wake up thins morning and I was literally running to the restroom like I always do on day 2 because I usually have a heavy flow. When I sat on the seat there was a light quantity of blood mixed with my urine and usually it's all read. I'm sorry if I am being too specific I'm just concerned, this has never happened to me in my 28 years of life. Now I know what you are thinking. "Well duh your pregnant" well I can't my husband got a vasectomy like 4 years ago and that was the end of our baby factory. But what could be happening to me? Please I am all ears to who ever has gone through this. I will keep posted to who ever is interested. Thank you.