I've tried pretty much everything but he still hasn't pooped. I've been told to look for black spots on his stomach and I have checked every day and there is none. He still eats like normal. He just hasn't pooped.
Give him a bath, while soaking rub his belly from front to back gently. See if he starts to strain or push, might come shooting out. If he does poo, see what may have caused the clog. If the urate is big, touch it with something to see if it is hard or soft.
A hard urate usually means to much calcium and/or dehydration. Only dust once a day lightly if they are under a year old, over a year 3x a week. Try giving them a bath a few times a week until the urate becomes normal again.