Apple watch battery, and unpairing from phone

The battery on my watch discharged super quick today, and I discovered it had unpaired from my phone. I tried to re connect, and it just would not work. I have turned aeroplane mode ON/OFF, reset bluetooth all to no avail. As a last resort I tried to unpair my watch from my phone, which was only 50% successful, they unpaired, however will now not re-pair, my phone keeps stating my watch is already paired to a device, even though it is not. Any help would be greatly appreciated.

All software is up to date, I am using an Iphone X, and series 5 watch with GPS and cellular.

Thanks.