Hi my tiny Mexican breed would be between day 56-60 pregnant but was scanned at 4 & 5 weeks empty.

She has acted pregnant throughout but never gained a belly her ribs seem wider but she seems smaller in the waist if anything but firm

The past few days she has been nesting at night time yesterday she was losing a fair amount of clear non offensive discharge, she seems really interested in one of my males almost flirting with him and he and another male are teeth chattering (taste testing) her pee, her vulva has swollen and is soft just as if she was near puppies coming.

I have a good feel of her belly and cant feel anything her belly feels a little hard swollen under the ribs but can't say I have ever checked there before?

I spoke to scanner who says she is ,99% sure no puppies hiding in there, does anyone have any experience with a phantom like this, I almost want to sleep downstairs she almost had me convinced something was happening last night but hasn't bothered today a bit of nesting when changing bed or sofa but seems herself and eating etc.

Is it worth getting a xray I haven't been temp taking if I go for another ultrasound will I know for definite. Should I wait and see?

I have your breed, and have bred many litters.  Usually mine whelp on day 56.  They are terribly prone to uterine inertia.  As they have such small litters, I've had bitches that didn't look pregnant, and 2 pups move down from behind the rib cage shortly before whelping.  Which is why I agree that you are probably best sleeping with her.  And I wouldn't keep feeling for the pups now.

There is nothing to lose by having an x-ray.  It's what I go for in preference to a scan at this late stage, as scans don't give you an indication of size.  At least an x-ray would confirm the size of any pups.

You will have to keep entire males well away.  If they're around when she does whelp, she could be post partum mated.

Why don't you get her x-rayed now, to confirm empty - I would.