Happy 5 month birthday to your lo! My ds will be 5 months next Sunday.
He got his first teeth a month ago and he had a number of symptoms - chewing on anything he could get into his mouth, fussing at meal times, red rosy cheeks,waking up at night (every couple of hours, wanting the paci), nappy rash, feverish, but most of all DROOL...constantly.
Just after that he got bronchiolitis - 'tis the season for it in the UK apparently. I would suggest that you get him checked out by your dr (if you haven't already) to make sure if it is a cold it's not settling into his chest (I'm not trying to scare you, don't panic!). If it is a cold our chemist said there wasn't much he could be given (Calpol or similar if feverish and Karvol - a eucalyptus capsule to sprinkle on a hanky and place under the mattress to help breathing).
The sleep thing is soooo frustrating - I was getting smug with 11-12 hours uninterrupted sleep but that's gone out the window. When he's not teething or sick he does sleep right through but it has taken time for him to settle, and he doesn't seem to remember that mummy had been comingto him every time he shouted at night...hopefully your lo will settle likewise.
Big Hugs - it's not easy this motherhood thing, is it?