I first went to Hoth at 38, it was a bit hard, so I PvP'd to 40, and got my L40 PvP gear, came back and stomped the place, I finished Belsavis at 45, I did half of Voss and was 48, then I finished my class story in Correlia, and went back to Voss to start finishing all of that where I hit 50. I did about 5 levels total of PvP while levelling, but I also skipped nearly all bonus series and I also skipped almost all heroic quests, I did like 2 flashpoints while levelling, of which one was esseles, so even though I got a lot from PvP I skipped a lot of other things, so I'm not really sure how you're hitting voss and still so low