you probably just didn't realize how iron decificiency is generally determined.
You said you went to your regular check-up and this is when it was discovered. How was it discovered...because as part of annual check up they ran b/w...i.e. CBC?
A CBC checks for many things of which red blood cells/hemoglobin levels is one. When you're not absorbing iron well, this is impacted.
With all the IVF treatments you've had across multiple clinics you had to have had a CBC along the way because CBC is routine to have on file prior to surgery and going under general anesthesia. You could pull your records from all of the clinics and see what your CBC levels have been at each check. Also a clinic may not have run a CBC if they had one on file from a prior clinic and it was within X number of months.
Or if you do go for regular annual check ups have your PCP give you the b/w results from prior checks and see what they show. Some people can be iron decifient suddenly vs. chronically. So just because you just got this result does not mean this has always been the case. And possibly why no RE has mentioned anything.
You know I know the overwhelming and angering feeling of wanting an answer and a reason.
But if you think this could be a contributor, get your prior CBCs and see if in fact this has a pattern for you.