My cat has a weird problem with digging at himself?

My cat is about 5 or 6 and he's digging at himself. He's been doing this since about 3-4 months ago. Back around that time, my people would scratch his back/tailbone and he'd lick the air. Now it's around his shoulder bones and his sides. He's digging at his skin and there's a lot of fur coming out and getting onto his claws. I've checked for fleas on him, and all I seen was a little bit of flea waste. It's not very noticeable, but I'm really worried about him. He HAS been around one cat with feline leukemia, but that cat got put down by one of my neighbors, and I don't think my cat and that cat made contact. My family is really too poor to take him to the vet and get him checked, and I highly doubt that he's up to date on all his shots. So if anyone could please at least give me some type of information that might be wrong with him, thank you!