I am feeling super stressed as my dog is on day 64 and although in stage one labour it’s going on for what feels like forever.
She has been off food for a few days.
Body temp down to 36.9
Sleeping most of the time with some panting and nesting.
How long can stage one last, think I am stressed as it’s bank holiday tomorrow so not my usual vet.
Also she has had 2 previous textbooks litters on day 61.

What is day 64, day 64 from exactly?  Unless you know ovulation or the onset of diestrus, it's not possible to have an accurate whelping window. 

When did her temperature drop occur?  You want to see the first visible contraction within 36hrs of the temperature drop.  Has she had any contractions?  You then want to see a puppy within 2 hours of that first visible contraction.  When you get sustained, frequent contractions, then you want to see a pup within 45mins.

And when you say 'going on for what feels like forever', how long has stage 1 been going on for?  The 1st stage of labour can last up to 36hrs, sometimes as long as 48hrs.  It does not include visible contractions - as soon as you see contractions, she's into stage 2 labour and the above applies. 

If you want to speed things up, try getting mum to move around a bit, even a quick walk round the garden.  Or put her in the car and have a drive round the block a couple times.

Day 64 from 1st tie
Thanks for your reply.
Noticed temp drop yesterday morning.
Puppies all moving around.
Stomach much lower today than before.
Also just noticed egg white like mucus coming from her privates.
So I am probably stressed for no reason. I took time off work from day 60 so that I could be with her all the time, maybe that’s why an hour feels like a day right now!

Note - with MY breed ..... I let mine go 2 days over (from the first mating) and if nothing had happened, involved my vet.   I didn't set much score by temperature taking although would note when it dropped, and stayed down, expecting labout to begin within the next 36 - 48 hours.  

Try not to stress - easier said than done I know but you stressing won't help her.   You should be sleeping in the room where her whelping box is, with her sleeping in it now.  I feel for you if your regular vet won't be around ....... did you speak to him about a locum or alternative should you need one?   Most vets in the UK have a Service who will pick up your call to the normal number, take your information, call the on-duty vet (who may be your usual vet as was the case recently when I had a panic situation) who will call you back.

Just try to find other things to do - the apple won't usually drop until it's ripe.  It's if she goes into labour and you don't see a puppy delivered after 1 HOUR (each delivery) that you need to get moving (vet).

I think if you've just noticed the egg white mucous, that is probably the start of things and you won't have long to wait!

Thanks so much for your advice.
Wait was horrendous but 7 beautiful healthy puppies born late last night!

Congrats!