Severe dehydration; what can I do?

I've been fighting this dehydration problem almost a week. I've had this problems for years. I've been worked up for it and they find nothing! I went to the ER and their only answer is anxiety. And it's not, I know and I have no insurace so I have to stay where it's cheap or free. It starts like this: I don't drink enough, then I get to start feeling funny. Sometimes I ignore the signs because I'm so buzy.
My heart starts to beat to fast, I get pains in my left shoulder and in my left arm and to the left hand and I'm feeling thirsty. By now I could kick myself in the butt because I do it way too much. Coffee & tea(except green tea)always does this too me really fast so I try never to drink it. When I get to where I am having these symptoms, I start drinking and the problems go away but if I stop drinking, the symptoms return so I drink more, then I stop and the symptoms return and this goes on and on. I try to drink even more before bed time thinking maybe it won't come back during the night and I keep waking up with all those same symptoms. The longer I don't wake up, the faster my heart, the more crushing the arm pain, oh and I forgot to say I also get pains in the head too(so that's about 4 symptoms). When I go to the ER, I don't go when the pain is real bad because I'm afraid too. When I do go, it's not bad enough to get a diagnosis. Sometimes they say stop drinking so much, that I'm washing my electrolytes out. But when do I know if I have drank enough? I went to the ER yesterday and they gave me an IV for a while, I felt better, went home and went to bed, woke up this AM feeling like it's starting all over. They said there was nothing wrong with me. Why can't they diagnose anything?

Like last night when I drank all day, different kinds of liquids like water, think powdered milk,
gatorade, Lipton Green tea, then I went to the ER, they gave some of the bag or liquid in my vein, sent me home, I drank some more before bed, slept all night, woke up it starting all over AND
my pee was really consantrated and I didn't pee but maybe 1/2 c and the symptoms have already started before I woke up, I'm sure that's what woke me. I've drank so much today and I've taken two 81 mg aspirin, Safeway Brand from Safeway grocery Store.