In my experience that’s dehydration. Modafinil is a diuretic, and appetite suppressant. Not only are you taking on less water because you’re probably eating less but your body is expelling water at frightening rates.

It's that or I think a lack of choline can also cause it. Cheapest and easiest solution is to eat some eggs.

That may be true to some degree, but I have also had them happen while purposely chugging water. My migraines are kind of cyclical as well. Could be coincidence.