Optimum weekly transdermal dosage

I suffer from Depression and anxiety, and have found transdermal magnesium helpful, but I seem to be load sensitive. I haven't been using it long, but I find I benefit more from using it only 3-4 times a week rather than every day. I find if I use it every day that I am less likely to get a relaxing response, both immediately, and for the next day. In fact sometimes it makes me agitated.

I am thinking perhaps I am getting too much magnesium building up in my blood if I use it every day. Has anyone else experienced this?