What can cause magnesium deficiency in an otherwise healthy person?

So I (23F) have been suffering from a magnesium deficiency for a while now. I just didn't realise that it was a magnesium deficiency until I started to take magnesium supplements since last week and my symptoms are starting to get better. I'm happy but what could've caused this deficiency? I don't have any other conditions. I checked my thyroid, blood sugar, haemoglobin, creatinine and everything was normal. My diet is good though I have been suffering from sugar cravings which cause me to binge and I also found out that sugar cravings is a sign of a magnesium deficiency. The only thing I can think of is that I've been a bit stressed for the last few years because of certain familial and financial issues. Could that stress have caused this deficiency?