Do you want him sleeping in your bed? If not, you need to stop bringing him to your bed because if you continue this course he will come to expect it. I'm not saying there's anything wrong with bedsharing; I'm just saying that the longer you continue this trend the more he will grow to expect it. It will be the norm and it will be what he has to have to go back to sleep in the middle of the night.
Is he waking and coming into your room or is he waking and crying? If he isn't coming into your room, give him a few moments to try and sort it out and go back to sleep. If he is coming into your room, take him by the hand and silently and gently walk him back to his bed and tell him "It's night night time. I'll see you in the morning."
If you feel like you absolutely must go in and check on him, make sure you are as quiet and plain as possible. Go in, give him a pat on the head/back/belly and say "It's night night time. I'll see you in the morning". For some kids this works. For some kids this only increases the anxiety, wakes them up even more, and then next time they wake they'll cry out for you again for help on how to go back to sleep. Keep in mind that he was capable of sleeping just fine in the crib so he is perfectly capable of doing so in his new bed.
Maybe go to the store and pick out a new stuffed animal for him to snuggle with in his new bed. Tell him the animal will watch over him and keep him company at night and if he wakes up all he needs to do is give the animal a hug. Otherwise, if he's healthy, not sick, not in pain, and not in danger, then you need to let him figure this one out even if it does mean a bit of crying on his part. The crying is because he wants YOU to run in and give him attention.