How old are you, OP?

As I understand it, changes in your menstrual cycle in late 30s signals that the hormones/balance that regulates menstruation are no longer working as efficiently as they used to do when you were younger, but you are probably still fertile (just not as fertile as before).

No good answer, but have you done an HSG? All my levels were normal too but because I had a prior pregnancy my doctor didn't want to do HSG. I ended up conceiving after that.

What does it mean when your periods have gotten lighter (but cycle length is the same)? My cycles are every 26-28 days, but my menstrual flow has gone from an average of 5-6 days to 3 days over the period of a year. Basically my period is completely done after 3 days. I am also experiencing prolonged infertility (been TTC 18 months with no pregnancy). All my initial infertility testing has been normal in terms of hormone levels.

I have done several medicated IUIs that have failed, and my lining has always been "excellent" on ultrasound for these IUIs. So at least up through ovulation my lining is normal.

Any thoughts about what light periods might mean in terms of infertility?