You're at high risk of developing severe dehydration!
This constitutes a medical emergency.
Please consider getting to the ER asap!
The consequences could be from serious to life-threatening,
such as seizures, hypovolemic shock and more.
If this is very recent, then it could be a stomach bug (gastroenteritis)
and if longer, then it could be a number of different things which should be explored.
Try to take at least teaspoon of water with a pinch of salt and sugar every 15 minutes, until you get to see a doctor.
Lightseeker has provided good advice.
Go to doctor they may need to check y OK ur thyroid bc I had the same problem and it was hyperthyroids got meds it was better