It's 11.45pm and 6mth old pup has been whining for an hour..

[pantsjustpants]

We're at breaking point. Literally don't know what the hell to do. We're both exhausted.... Please help

Hi, sounds like you're having a tough time of it and no one has come along with advice. I'm no expert I just have a little bit of experience with our 12 week old pup and some stuff I've read here and there.
Where is your pup kept? Has s/he been gradually introduced to that area, with positive rewards and treats to associate with the area. Has s/he been allowed to go in and out of there during the day? Has s/he had a gradual reduction in her/his access to you at night? (eg bedroom then hallway then kitchen with doors open and then closed etc.)

Also have you taken him to the vet to rule out any medical issues?

How are you both this morning? If this is a new thing I'd go to the vet and get him checked out