What Causes Dryness In The Throat And Under The Tongue?

Hi can you help my throat and under my tongue is very dry and I can t sleep I just check my urine it s very clear I try water it did work about two hours ago I was laying down trying to sleep, out of no way my heart stated racing I jump up really scared, than throat and tongue began to dry I drank water to keep my throat and tongue from being dry i laid back down try to get some sleep than out of no way I began feel hot and shaking and scared I had to turn on the air conditioner that help for the moment than I try to sleep again I stated feel strange it felt like my body was shutting down my heart started racing again I tought I was going to have a heart attack it felt like I was dying I say oh I know my body is dehydrated I try drinking more water but it did work I remember I have a bottle of pediatric electrolyte I drank that it brought the dry mouth down some but my throat is still dry my under my tongue is still just little dry my sliver is retuning 70% what should I do next