Why is my turtle sick?

I am worry about my pet turtle because he is very young. Let me get right to point, I started to notice that he's skin had another layer on top of it, after that I started to notice he's eyes starting to swell up. Now he sleeps all day and doesn't eat. Just wanted to let you know that I keep him in 30 gallon tank, with a basking area, with no gravel and no filtration system. Can you help me figure out what is wrong with my baby turtle PLEASE!!!!