dedelite... there are iron supplements you can get that don't cause constipation. I also find that digestive enzymes and/or probiotics help alleviate constipation, as well. You might look into those. They're much better for you than taking laxatives.
How long were you on the previous doses of 50 mcg and 75 mcg?
Are you taking your medication as directed, with a cup of water, first thing in the morning on an empty stomach, then not eating/drinking anything for 30-60 minutes?
Hi dedelite... Both your Free T4 and Free T3 are too low in the ranges, so it's good that your doctor was willing to increase your levo dosage. Those levels could/would account for the symptoms you report.
I'm not sure why you think your vitamin D is "super low", as optimal vitamin D is about 50-60. You should probably be ready to switch to a maintenance dose of vitamin D now..
Your ferritin, on the other hand, "is" incredibly low... it should be, at least 60-70. Are you taking an iron supplement? You should ask your doctor for a full iron panel, not just the Total iron. Iron is necessary for the conversion of Free T4 to the active/usable Free T3.
What dose were you on, prior to being increased to the 88 mcg? It's a personal choice as to whether or not you switch to the Naturethroid. You may do alright on the levo; your levo dose just needs to be high enough to be effective. Perhaps the 88 mcg will do it; you'll know when you retest in a few weeks.
From the top, your ferritin is extremely low. Having adequate ferritin is very important for good hair growth. A good target is 70, so you should supplement with a good iron supplement like ferrous bisglycinate, ferrous fumarate, or ferrous sulfate. I'd say you should start on about 25 mg and increase every week or so until you get to 75 mg. Along with that you will need to take some Vitamin C or magnesium to prevent possible stomach issues. Your B12 and D are good. Why did you say D was low?
Your Free T4 is considerably below the target of mid-range, which is 1.3. Your Free T3 is actually below range, so how can your doctor ignore that and say you are doing well, especially since you are still suffering with hypo symptoms? I'd say you are directionally correct in switching to Armour or NatureThroid. Although if you can get the doctor to agree, he would probably switch you to less than a grain. In actuality, one grain of desiccated med is the equivalent of only 66 mpg of T4. So in view of your increase to 88, that would mean you would need 1 1/3 grains of desiccated. And in view of your low FT4 and FT3 I would push for a switch to 2 trains of desiccated and start with 1 1/2 for 3-4 weeks and see how you feel before considering going up to 2 grains.
If you try and talk the doctor into switching you and he has an issue with the conversion amount, you can point him to this link, which is the ATA/AACE Guidelines on Hypothyroidism. On page 1002 it states that T3 is 3 times as potent as T4. Since one grain of desiccated med contains 39 mcg of T4 and 9 mcg of T3, if you multiply the 9 times 3 and add the 39 you only get 66, which is the correct conversion.
https://www.aace.com/files/hypothyroidism_guidelines.pdf