A., do not, I repeat, DO NOT, bring him into your bed to sleep with you once he has been sleeping just fine in his own crib. I cannot stress this strongly enough.
He's going to wake up whether he's in your bed or not, but the extra steps and effort you put into going into his room are WORTH IT in the trouble you save by not having to break him of the habit of sleeping with you.
NO child, I repeat, NO CHILD, will sleep all the way through the night, all the time. You are very fortunate that you got a few months of uninterrupted sleep at night as is, but know that this will not last. All through his childhood, he's going to have times when he doesn't sleep well due to illness or nightmares, and then after a while, he'll go back to sleeping well. This is just part of the process of parenting a small child.
Now, as to why he's doing this now...he's past 6 months old, so he's probably teething. The pacifier helps soothe his gums, so when he wakes up in the middle of the night from the teething pain, he needs the pacifier to help him cope. This is normal. You're lucky the pacifier helps him as much as it does. As teething progresses, this may not be the case, and you may have to give him Orajel, baby Tylenol, or frozen teething toys in the middle of the night as well.
Expect him to wake you up periodically until he's a year old or whenever the first 8 teeth erupt. Once the first 4 front teeth are out, he's going to get canines and so forth. Look out for ear infections, gas pains, diarrhea, fevers, etc., at this time. All of these things will wake him up, and keep him up, at this time in your lives.
Sorry I don't have better news, but this is part of the process. Enjoy him in between bouts of teething pain and have patience.