You don't have to have full blown celiacs to be affected by gluten. I don't have celiacs but my blood test shows i'm a 'little' gluten intolerant. The lab range went up to 15 and my result came back as an 18, so i'm 3 over. My current doc has told me to go easy on gluten foods and to limit them in my diet. Apparently, whether you have celiacs or a moderate/mild form of gluten intolerance, the gluten can stop certain vitamins/minerals being absorbed.
You say that you eat meat so your low iron would not be from a vegan diet. So it has to come from something, somewhere.
The problem with getting your thyroid tested is that majority of doctors will tell you your thyroid is fine so long as your results come back 'within range' of what the lab says.
In the last 10 years my thyroid TSH has been all over the place, from virtually 4 back in 1998, back down to 1.something, then back to 2.something etc etc. It never stayed put in all that time. For 7 of the last 10 years i've shed abnormal amounts of hair and i kept getting the brush off by my doctor and even from 2 endocronologist visits some years back. It wasn't until i found a doctor who knew his stuff that he said my thyroid results are not normal, yet not out of 'range' sufficiently for most doctors to worry about it, but i a number of worrying symptoms and couldn't keep up my iron stores.
Finally i had a thyroid antibodies test done, which revealed i had an auto immune thyroid condition known as Hashimoto's. The doctor i'm seeing for my thyroid did further testing and found out my pancreas was having difficulty producing sufficient enzymes to digest protein. He found this out via a stool analysis test.
He then got me to do a saliva test to check my hormones as this is more accurate than a blood test. It is also done at home over the course of a day, where saliva is deposited into a small tube. I got 4 tubes and had to deposit saliva into them at 6am, 12noon, 6pm and 10pm. This showed that my estrogen was double what it ought to be, my testosterone was a little over what it ought to be and my adrenal glands were not functioning correctly. All this accounted for my weird menstrual cycles and the reason why my hormones were out. I've been on a herbal supplement from my naturopath to regulate my menstrual cycle, which has helped big time.
So now i'm on thyroid meds, enzymes for digestion and a tablet for my adrenal function. I'm still on iron tablets. My ferretin got to 61, but then i slacked off and at my next blood test it had dropped a little. I'm also on vitamin d drops, iodine drops and selenium drops.
The enzymes i take for my digestion are prescription only as the ones from the healthfood store aren't strong enough for my type of problem.
I've only been on all the above meds (except for the iron) for the last 8 or 9 weeks, so it's a little too soon to tell whether things have begun improving. I'm guessing it will take some time.
If i were you, along with getting your full iron study done again, i would get your vitamin d checked as well as your iodine. Usually if people can't keep their iron levels up and it's not due to some form of internal bleeding or extremely heavy periods, then it's malabsorbtion due to something which is going on in the digestion process or thyroid related. A lot of people with thyroid issues appear to have low iron issues and have difficulty raising their iron levels.
The next thing i would do is take your thyroid test results to the thyroid section of this board and see what some of them have to say. There are some very expert people over there who have been through it all and know what they are talking about. The other thing is that there are different form of thyroid conditions. You could be over or underactive or it could be an auto immune related thyroid condtion, which can only be determine when they check your thyroid antibodies via a blood test.
That's about all i can think of/suggest at present and i truly feel for you as nobody needs to go through the frustration of this, especially leading up to their wedding. At least you are doing your research now. I wish i had started sooner and not listened to doctors repeatedly telling me i was fine when i wasn't. Best of luck