What Causes Long Delay In Getting Period?

I am 32 years old and have not gotten my period for IDK how long, and for the last 4 years or so it has been so light that I have not needed to use anything at all to catch the flow. I have mentioned this to sevearl Dr. and all my blood tests they say are fine is there any thing else I can do to find out what is wrong. With all the research it seems to not be nornal