My 18mo has never been a great sleeper. However, the last week or so he's woken at some point during the night and it's taken over an hour of him crying on one or other of us to get him back down. Could be molars - there's definitely something going on there. Could be regression - though I kind of assumed that there had to be some decent sleep to regress from.
Please reassure me that this is pretty normal and won't last long - we're struggling here.