I know exactly how you feel. I've been working on my health with supplements for the past year, and there have been many ups and downs and lessons learned. It can be super frustrating when you have bad days, especially after having finally felt good, maybe after years of not feeling good. I want to feel good all the time!
B6 is also required to make serotonin and low B6 can make you depressed, and cause sleep issues, muscle pain, nerve pain, carpel tunnel pain, among many other things. Also, iron is also needed to make serotonin. Pregnancy can deplete B6 and iron, so consider trying both.
A word of caution, taking B6 can bring Iodine into the thyroid quick, and may cause hyperthyroid symptoms. You may find you need to go slower with Iodine if you add more B6. Hyperthyroidism is dangerous because it quickly deletes your stores of many nutrients. You can reduce your risk by eating coleslaw and raw cruciferous vegetables while you take B6. Keep extra thiamine and maybe some l-carnitine around just in case (but check with your dr first about l-carnitine if you're pregnant or breastfeeding).
Iodine is known to help with breast lumps, and it did help me, but adding B6 made mine disappear nearly overnight.
One more thing about B6, if you are breastfeeding, don't take more than 100mg a day (or ask your doctor), because large amounts of B6 may lower prolactin hormones which you need to make milk.
Another vitamin with a key relationship to iodine is vitamin A. It's also often depleted by pregnancy. And this is compounded by the fact that it's not safe to supplement much with vitamin A during pregnancy. Some say postpartum thyroiditis is from vitamin A deficiency. Vitamin A is needed for making white blood cells, and this could be one reason why yours are low.
Also, check out the research on children in India with goiter which found vitamin A to help just as well as iodine. Vitamin A is a tricky one because too much can be dangerous for the liver (if you've had a baby, you are most likely low in vitamin A). But not enough can be bad for every part of your body. We still haven't learned everything about how this vitamin is used.
If you plan to get pregnant again in the future, you would definitely want to supplement now with vitamin A (retinal palmitate), to rebuild your stores.
Low platelets are associated with low B12, low vitamin C, low folate. You can have your B12 and folate levels checked, to verify this. But it's a good idea to take extra B12, folate and vitamin C anyway.
Low vitamin D levels are associated with high MVP. You can get your vitamin D levels checked as well.