Youch, sounds like you missed a lot of bonus quests along the way. Most people I run into seem to out-level the planet they are on by some 2+ levels (exa. Hoth is 37-41, I see peeps there that are lv42-43 sometimes). Best thing to do if your skipping that many quests is to just hang out in the fleet for a few days and just run a bunch of flashpoints. As a tank you should be able to start some up pretty easy. Space missions are hellafun and almost feel like an exploit with the amount of xp they give.