What Causes Excessive Thirst And Increased Appetite In A Child?

Hi, I have a 2 year old son who lately seems to be drinking a lot of fluids and peeing a lot in return. We put nightime diapers on him and he often wakes up soaking wet from leaking out the dipaer. There are times recently he has awaken and asked for something to drink. He has been irritbale and very moody. He has never been a napper but in the last few weeks he is taking 2-4 hour naps and is still irritable. He is eating like crazy. He was DX with Asthma in December of this year he also has pretty bad Ecsema. He takes Claritin dialy to help with the ecsema and has an inhaler PRN. He has been getting red rings under his eyes also. I am hypoglycemic and diabeties runs in both sides of mine and my husbands familys. Could my son be showing SX of diabeties? We have no health insurance so I want to do as much research as I can before I take my son for a costly visit. Thank you for any advice.