You may also want to try and "reintroduce" the crate to your pup by making it a fun thing for him to get in and out. When I was crate training my chi, it was suggested to get a toy for the crate only, kind of like a teddy bear for a child.
Also, kongs are fantastic time-consumers and great toys for dogs. If you don't know what they are, you can find them at petstores - they're hollow so you can fill them with food, treats, whatever - and will give the pup something to do while he's in the crate. I fill our kong with kibble, a treat or two mixed in and a smidgen of peanut butter.
The suggestion of the hot water bottle is a great idea - you can also buy disks that you heat up in the microwave and they'll stay warm for up to 8-10 hours. Just slip them in the bedding and you're good to go.
Another thing is if he's 6 months old and you're gone for over 5-6 hours at a time, he can't hold his bladder that long, so he's going to have no choice but to go potty in the crate. If that's the case, he's got a negative impression of it and you may need to get a new one, different make and model so he'll "accept" it better. If he's peed on his actual bed, he may not want to lay on it due to that fact. Most people on the board with small pups confine theirs to a bathroom or part of the kitchen were there's plenty room for a bed, a potty pad and their food so one doesn't infringe on the other.
The main thing is you want the crate to be fun for your pup and, from what you described, it sounds like he's not looking at it that way.
I'd try putting toys in there, a kong and maybe even turning on some soft music for him to see if that makes the experience more pleasant.