Frequent urination and burning while passing urine could be a sign of urinary tract infection. You will need to do a urine culture and sensitivity test and a routine urine examination to look for pus cells. And if signs of infection then you may need antibiotics.
Health Tips
If despite your water intake you are feeling dehydrated you need to increase your volume of water intake. Make sure to drink 3 litres of water a day. As it is summer you might be sweating more so please make sure to have more fluids.