The same happened to me when I was age 22 after I caught an STD. The menstrual cramps hurt more after I caught the STD. Nevertheless, it could be stress, age, and other health factors. Most likely it's stress.
I had the same problem in 2010 where I thought it was a period because of the cramping, but come to find out I was pregnant and it was implantation that was causing the bleeding and cramps.If the blood is anywhere from a light pink to a dark brownish, except bright red, it could possibly be. There can also be many other factors that can xause thst such as stress, cysts, etc. If you're concerned I suggest calling an OB/GYN .
sometimes it was stress that makes the period like that.