26 mth old scared of sleep!

Hi all

we need some advice on our 26 mth boy the past 6 weeks have been shocking and last week we got about 10 hrs sleep in 1 week. We both work full time and have a 7 month old. Who sleeps through the night but now with his older brother not sleeping he is now waking too!! Last night we resorted to DS1 sleeping in our bed and he slept all the way through. And tonight he screamed for 40 mins, then when we put him in our bed (way before our bed time) he's out to it and with our bedroom door wide opened!! My only problem is I don't want him to get used to it... and what is triggering this behavior? We have an apt with an ENT specialist tomorrow as his adenoids are enlarged so he may need these removed. Which We r hoping will solve this no sleep issue and he does also have a bit of sleep apnea. . So long story short what do we do??