I have a 6 month old bulldog. Up until about 2 weeks ago, he slept all the way through the night in his crate. Now he has started waking up 1 or 2 times every night, barking. I bring him outside and he pees. Then I put him back in his crate. I don't understand why this suddenly started happening. His schedule for eating and exercise has not changed at all. Hopefully this is just a phase that he will grow out of?? I'm exhausted!

Have him checked for a urinary tract infection. If he is clear, then he may have figured out that he can go for a middle of the night romp.
Play with him extra hard for half an hour or longer before bedtime. If he starts barking ignore him (Yes, I can hear you laughing from here). Honestly, if you let him bark for a while and give in, then he has just learned that if he keeps at it he gets what he wants. Behavior that gets rewarded gets repeated.
You may need to put him in a different room with a radio on low and you may have to use earplugs for awhile.

Next time he cries just ignore him. My dog used to cry to go out when he was a pup to. I always let him out but then my vet told me I was only encouraging him to get in the habbit of going out late at night. This could just be a habbit and the best way to break it is to ignore him.