
If we ever had a phantom, which was rare even if the Basset is 'maternal' (even if they can go to secondary inertia the moment they feel pain!!) it didn't start until after the bitch would have whelped. Certainly not during the early stages of pregnancy!
You have to be patient. If it was meant to be, it will be. Plan for a litter and hope. It won't 'kill you'.

I have never done all this scanning - the only investigation I did was if, a couple of days beyond the 'due date', nothing was happening, I'd have x-rays done if the vet himself wasn't cure whether the bitch was empty or not. And sometimes with my breed with the well-sprung ribcage, any puppies could be hidden up under the ribs until they finally drop ready to be whelped. By 7 weeks, puppy movement should be seen. That still gives the breeder 2 weeks to prepare.
ps A tie isn't always necessary for a successful outcome - much as breeders prefer to see one.
ps A scan will only confirm a pregnancy, or not, at the time of the scan. And if you are told no, my money would be on you still waiting 'just in case the scan was wrong'