I'm 20 yrs old and my period comes every other week or sometimes
Can last up to a month. It's been going on like this ever since I got
Married two years ago. I was still sexually active before I got married
But my period was normal. Does anyone know why this is happening?

I also have no children and I'm not under and kind of birth control.

You will need to see your OB/GYN about this. It could be causing you some severe anemia.