I think you can stop looking for babies. By this time if your goats' vulvas are not puffy and if the udders have not filled they are not close to kidding and are probably not pregnant at all. Although I raised goats for many years, I never figured out the ligament thing. However, shortly before kidding, the tailbone gets loose and it seems to raise up from the rump and you can actually slide your fingers underneath it. If you stand behind a doe, clasp your hands together just in front of the udder and push up sharply, you can feel the kids, if there are any, as they come back down.
Dairy goats are seasonal breeders. They usually start coming into heat in September and cycle through February. I have had does come in as early as August and I have bred does as late as March, but you can't count on that. Boers may breed year round and Nubians, since they originate near the equator, may have a longer breeding season than Swiss goats (Alpine, Saanen, Toggenburg, etc.) but you can't count on that, either.
Just so you know, mounting behavior may or may not be a sign of heat. Goats mount each other for any number of reasons.