80-90 is probably lower then many drink on here actually. Are you having any caffine, tea, diet drinks or suppliments with dehydrating ingredients which can make it worse?

Water helps flush toxins from your body and can help weight loss. For water intoxication you would have to drink more then 80oz, and do it all at once really fast in one setting.

Since you do have alot of water, or get leg cramps as syd, it could be because alot of electrolytes ar ebeing flushed. A pottasium suppliment can really help, as can supplimenting calcium and magnesium.