My 8 month old is currently going through a regression along with teething. He is just not sleeping at night time. He goes down in his cot fine, but starts to wake up constantly during the night (like every 15-20 mins). He will only go back to sleep if I pick him up. Once I put him back down he wakes the moment he realises I'm either not there or he's back in his cot and starts crying. Does anyone have any tips to help at all because I've gone 3 weeks on very little sleep now and I'm completely exhausted.