How to treat Hyponatremia?

So yesterday I had to go to the ER because I felt really sick, tachycardia, faint/dizziness, and weak. So the PA said it was due to dehydration which is odd because I always drink the recommended amount of water that my body needs but right after I was put on IV fluids I felt a little better but then got a huge headache and I still have a headache. But when I drank some water today I got really dizzy and started to feel the same symptoms of yesterday, so I'm pretty sure I have the opposite (overhydration), plus I haven't been eating normally and I'm pretty picky about eating high salt foods because I have anxiety. So does anyone know how to correct this? If you've had Hyponatremia what was your experience like? Help girls!