How long have we been on the road, and have we started/ended in Rasheman?
If you were hired on in Rapola as a caravan guard, you've been on the road just over two weeks (It takes 20 or 21 days on horses to travel between Rapola and Eyrrinberg).
Though traveling from Rapola to Eyrrinberg or Niðarós wouldn't get you back to Rashemen, either one is on the way back to Rashemen from Rapola. For a real world example, it would be like traveling from Nizhny Novgorod, Russia, to St. Petersburg, Russia, when your eventual goal is to cross the Baltic and get back to Sweden. (Though in mirror image, as you are heading east, not west).
You could easily have gotten to the area from somewhere to the south (there is a lot of "Norseness" south of where you are, including Birka and Uppsala), and were just planning on heading back east toward the coast to catch a boat across the Ashane Sea to Rashemen.