I need answers

My ACTH stim test result came back normal. It was ordered because I consistently had low am cortisol over 10 months. In December 2023, it was 5, June 2024, 3.3, and September 2024, 4.1. I also got my ACTH tested for the first time this month, and it was 8.1 pg/ml.

If my stim test is normal but cortisol is low, then there must be some underlying issue. It doesn’t look normal to me, but my endo told me to wait for 4 months and get tested for cortisol levels again. It is very unsettling to me. What can I do to find out what’s causing my morning cortisol levels to be low and potentially fix it? My DHEA is in normal range as is tsh(under 1.5). I'm not on any steroids.