Okay, couple things.
1) Your gecko might be in shed, and it's probably having difficulty shedding because you don't have a humid hide. They need a place with high humidity levels to allow them to shed properly. Get a tupperware container and cut a hole in the side or top (make sure there are no jagged edges). Put wet paper towels in the bottom and place it in the middle of your tank. Make sure the paper towels stay wet all the time.
2) You must monitor your temps. Either get two digital thermometers with probes and set them on the floor of the tank (one of the warm side and cool side) or a temp gun. Reptiles can't produce their own body heat, so they move between areas of different temperatures in order to maintain proper body temperatures. Leos should have hot side temps of 88-93 and cool side temps 10-15 degrees cooler. There needs to be a hide on each side so that your gecko can move between the two sides while still feeling safe.
3) What's "dry food"? They don't make dry food for leos. Whatever it is, remove it.
4) You need supplements. Absolutely crucial, or your gecko will eventually develop Metabolic Bone Disease (a severe calcium deficiency) and die. The best way is to get this: T-Rex Leopard Gecko Calcium Plus Supplement Reptile Food Supplements Take a plastic bag, put some of the powder in, and then put the crickets in. Shake them around until they're covered, then feed them to your gecko. Do this every feeding.
5) Get rid of the sand. Some geckos have been known to ingest it. If it's calcium sand, it's very, very dangerous for them. Replace it with paper towels, but make sure they are weighted down so that the gecko can't crawl under them and burn itself on the glass where the UTH is.
If you fix all of that, I'm sure you'll have a very healthy, happy leo. Do you have any pics? It would be good if we could see what kind of condition it's in.
~Maggot