R.C.
Hi A., have you tried the dreaded Cry it Out yet? It might be the only way for him to actually go back to sleep- that is, if he was previously a good sleeper. Our nearly three year old has GI and reflux issues and has never slept so crying it out for him never worked and ultimately we would just bring him into bed with us in the middle of the night until we got him a double bed and we'd go in there when he called instead.. still working on issues. That being, our new baby is a really normal sleeping baby despite similar problems, as a result, if I can't figure out what's going on with him (teething, gas, etc) i let him fuss/cry and generally a half hour later he is back to sleep. I juts turn the monitor down as low as it goes...
Are you sure its teething? if so, it will eventually pass and take a while to get back on track with sleep habits. if its bad belly or reflux it might be worth checking out with GI doc. Good luck!