Sorry to hear that you feel so unwell.
You mention Iron & nutrients but what about adrenal issues.? If your meds haven't been working properly you may have compromised cortisol levels. When you don’t make enough cortisol, thyroid hormones can pool high in your blood and your body responds by converting the T4 to excess RT3.
Low cortisol levels and high RT3 can cause chronic anxiety, poor coping skills.
What about insulin & blood sugar levels and any gut issues? IBS or candida ?
Do you have low stomach acid or malabsorption issues?
What about female sex hormones? Is your monthly cycle regular or are you menopausal?
Do you have a high thyroid antibody count ?
Any of these can impair the synthesis of thyroid meds.
Approximately 85% of circulating T3 is produced by monodeiodnation of T4 and the small amounts converted and unused are usually eliminated quickly by the body. You are taking a lot of T4 to feel so unwell so must assume some is possibly resulting in high RT3 which could bind to the T3 receptors blocking the action of further T3.
When too much RT3 is produced, it becomes a vicious circle as the RT3 competes with T3 as a substrate for the 5-deiodinase enzyme and will inhibit the conversion of T4 - T3.
Taking less T4 and more T3 will help eliminate RT3 from the body and encourage T4 to convert.
However T4 is not always to blame for high reverse T3. High levels of T4 can lower D2 enzyme activity, which lowers T4 conversion to T3. But high levels of T3 will raise D3 enzyme activity, so more T4 is converted to reverse T3 to keep T3 levels normal. In other words, neither T4 nor T3 can be too high, or the appropriate enzymes are invoked to keep the levels where the body deems appropriate.
Eat protein at every meal as it helps to boost T3 and also convert T4.
Supplementing selenium is known to help with T4-T3 conversion.
It is important to take your meds on an empty stomach with a glass of water, 1 hour before food, 2 hours before supplements and 4 hours before calcium, iron or vit D supplements.
If this were me I would reduce T4 & increase T3.
This following link explains the importance of vitamins and where they may be obtained. This forum is supported by the charity ThyroidUK. You do not have to join the charity to benefit from this forum but by doing so you will be supporting the charity and also entitled to various discounts when buying supplements, as detailed in the link below.
High T4 & RT3.