Your experience is not unusual. I had similar experiences with severe dry skin. I would take Mg and become more dry then take calcium, get better, then seem to get worse again from too much calcium. All that seems to have stopped now that I am using the iodine.
It is possible that you were having a calcium storage problem. Funny thing about calcium, and Mg for that matter, is that deficiency symptoms and toxicity symptoms can be quite similar. You may store calcium and need magnesium to metabolize it, but you may also have a mineral deficiency that is antagonized by Mg. It could be copper, potassium, iodine, the list could go on. It is important that you find that missing nutrient. Also, I have read that vitamin D deficiency may have a contributing factor to MS. Vitamin D also has a major role in both calcium and Mg absorption and usage in the body. That may be an important link for you to investigate. You may need substantially more than the usual RDA to restore balance, but PLEASE research this extensively before doing anything with it. I only provide information, not medical advice, but I hope that something I've said will help.