Sorry to hear you had a PA at work today
. I imagine it was pretty scary.
However, water intoxication/hyponatremia is very, very rare. I mean you'd have to drink essentially 2 swimming pools full of water to even break the surface of having either one. Was the water you had to drink cold per chance? Sometimes cold drinks can induce quick headaches. If not, they're probably completely unrelated. Either way, I know you'll be just fine!