If he's only got 6 teeth then I'm not sure why you're assuming it's not teething. Many kids get 8 teeth by 12 months and 4 molars between 12 and 18 months. Their jaws can hurt as the teeth are coming up, not just as they break the skin. I've read that analgesics (acetaminophen, ibuprofen, etc...) aren't proven to help pain in babies and toddlers. You're better off using something homeopathic like Arnica or Hylands Teething Tablets. You can try Orajel, but it's really just a topical solution, it doesn't help down in the jaw if that's where it hurts. Besides, you have to use a TINY amount because it can get in their throats and make them choke when they can't feel the need to swallow.
I found "The Baby Whisperer Answers All Your Questions" when my sons had sleep issues after sleeping fine.
Have you changed anything in his diet? He shouldn't be on milk yet, but he could have cheese and yogurt. If you started those maybe it's a dairy protein issue.
Good Luck:)