Teething and cold are definitely two good reasons that might ruin his sleep. Have you given him any calpol? I didn't give this to my DC1 until he was a year old, but in hindsight should have probably given it a bit more often / earlier to give some pain relief when he was teething.
My 9month little boy has always been a good sleeper at night but the last 3 nights he has been really difficult to go down and has been waking up approx every 30 mins screaming/moaning! Then goes back down with comforting him. He does have a cough/cold and teething. As I am a first time mum this is all new to me, does anyone have any ideas, is it illness and teething related? I hope it passes! Please help, many thanks cx