Are you taking Iodine as well?
Important to not take just one element in high dosages, without the supporting ones.
Magnesium, vit C...etc.
Could be detox of fluoride you are going through, but I doubt it in such a short time.

One symptom I can relate to is dry skin, this happened to me when I was hypo T. Borax aggravated it back then, but now it doesnt anymore. Unless I take a lot / too much

I dont recommend Mule Team internally, the chance of it having inpurities or additives are to big for me.
In most cases it works out well, but I wouldnt do it.

To avoid fluoride I have been brushing my teeth with a combination of baking soda and borax for about five months. Initially I used half baking soda and half borax, then I used one third borax, and now I use about a fifth borax and four fifths baking soda. I try to rinse most of it out of my mouth after I'm done brushing. I wet my brush and then set it on the powder, however much sticks to the brush is how much I use. It seems to have a smoother feel and better taste than brushing with just baking soda. I have bleached my teeth a little fairly recently and they look quite clean after I brush.