Sonya looked like that 2 days before she foaled. Pretty tight and not very much milk. She waxed up 5 days before she foaled, and started leaking-like you could see the milk coming out from 10 feet away- 2 hours before she started foaling. She urinated over 20 times within 10 minutes.
Good luck and I am hoping foal a foal in the next 48 hours!