Premenstrual spotting with no diagnose yet

[jori]

I am a 42 woman with a 5 day premenstrual spotting.
I have been to numerous doctors appointments and so far don't have an answer. My blood tests are fine, no premenopause, no thyroid issues, no infections. I don't eat gluten/alcohol/dairy/sugar...
I have also tried progesterone 200mg but it did not change the spotting.

I am trying to get pregnant through IVF and I am afraid the spotting is a symptom of something that might affect an embryo implant during IVF.

I don't know what else to do to reduce it...

Thank you!
Jori