Maybe you have finished the latest planets a bit to quick, so you ended up in Belsavis early in game. When you start doing all them q's available there + your classquests, you should be allright with getting to level. If you don't have enuf lvl yet to move to new area, just go do some Flashpoints. For sure you will gain half a level if you do 1 or 2 flashpoints (depends on how long they are)
Also, these Flashpoints reset every day for you, so you can do them every day untill your level is high enuf to move to new area.
Also, doing Spaceship-missions make you xp.
I had a bit of the same, at 42 I found it becomming a bit harder then the whole run upon that bit, but it was because my level was just a tat to low for the area. Also, at this point I got fed up with questing, but smelling the lvl50 made me go on, and now I am happy I pulled through, cuz at 50 it's lots fo fun.