Itching on the entire body. Problem!

After getting up in the morning since last 2-3 days and sometimes while just sitting, my thighs and area just below the knees and sometimes arms start itching. I experienced it the first time few days back, after an hour or so of taking warm shower. When i check, there are no mosquito/flee bites or rashes or anything else. Very rarely i have seen any redness or rashes in the area of itching. Earlier i thought that maybe it's happening because of dry skin but i applied some vaseline and moisturiser and it didn't seem to help much. Last night while trying to sleep itching started again. I have never experienced it in my life earlier though earlier during this winter season i used to apply some coconut oil on the entire body and this year while staying at hostel i rarely apply anything however when i tried using the body lotion or vaseline it didn't help me much. Also my water intake is quite low these days but not sure why i am facing the itching problem