Hi there
Didn't want to read and run as it is an awful thing to go through for so long and I truly sympathise.
I used to commute from Bedford to Croydon, so up at 5am returning at 7.30pm. whilst my lil one was up constantly from every 40 mins to every other hour for months.
We resorted to using the ignore for 5 mins, 10mins and increasing each time and it works within days.
Of course he then started to stand or climb out of the cot if we were'nt there. He was sharing our bedroom so used to jump up like a meercat at every noise and we also lived on a busy road with a streetlight near the window.
All I can say is that once you rule out teething, being wet/dirty and blocked noses, it may have just become a habit and probably in my case, him just wanting to see Mummy.
Our biggest mistake was that we allowed him to do it for so long that he used to get up in the night for attention or want to play. Our tactic then was to ignore him completely - again not easy as his cot was right next to our bed and we lived in a block of flats so they suffered with us but it worked quicker than we expected as he started to learn that it was bedtime and time to sleep.
We made sure there was no eye contact during the night or long lingering cuddles just straight back to bed if we did have to change him. We of course had the odd wobbles and bad nights but we soon got him to sleep through.
The magic word is CONSISTANCY from BOTH of you, as one or both of us used to cave in. Sometimes through sheer tiredness, my Husband couldn't hack the sound of him crying so pitifully but we taught him that night time was for sleeping.
Some may not agree with my response but I can only share what worked for us.
I now have another 17 month old - he is at the other side of the bed! He is teething so the last few weeks have not been so good but overall. He will wake and see us there and go back to sleep.
Things will improve I promise you.
xx