I would guess you either just have no magnesium deficiency or have some other condition which causes your symptoms unrelated to magnesium or prevents magnesium

I would guess you either just have no magnesium deficiency or have some other condition which causes your symptoms unrelated to magnesium or prevents magnesium from doing its job. A couple weeks is more than enough to feel serious difference. Another chance is you are using a form of magnesium which is not the best choice for you. It generally is recommended to try different. There are many.