although you have tried it, I do suspect magnesium deficit and have some questions that could help rule it out as a potential contributor to your ongoing problem:
1) have you measured your serum levels, and are they very high normal, eg 1.1 mmol/L? if so, I would start looking for other causes. if not, you could likely still have an absorption/retention issue going on.
2) did you boost your magnesium intake to 600mg per day?
3) did you include daily servings of mag-rich foods like swiss chard and spinach? (1 cup of either, boiled, provides ~150mg which is about 1/4 of the DAILY requirement if you are experiencing symptoms)
4) did you remove magnesium-depleting influences like coffee, alcohol, dark-coloured carbonated beverages (phosphorus), or high-dose vitamin d3?
5) did you try a supplement, and if so,
a) what form was it?
b) how many mgs of elemental magnesium were provided per serving?
c) how many pills per serving?
d) how much did the elemental magnesium contribute to the daily 600mg target?
e) did you try an insoluble form like magnesium oxide? or a soluble one like magnesium glycinate? many magnesium supplements are notoriously ineffective when it comes to absorption. magnesium glycinate would be the wiser choice.
my approach: no meds so far - just nutrient-dense anti-inflammatory whole foods, and supplements where needed
info: www.whfoods.com, www.nutritiondata.com