As GFreeGamer stated, Jedi Shadows bloom kind of late.
A lot of people who played during Beta had said they were going to do the first 20-30 levels as Balance and then switch to Infiltration (those who were ultimately going to be Infil anyway).
Infiltration becomes quite good once you get talents like Masked Assault and Circling Shadows. There's some other good ones down the line, but those 2 really help with not depleting your Force pool so quickly.
If you remain Infiltration spec'd (I'm assuming you are playing Infiltration), don't forget to use Saber Strike. It does diddly for damage, but it beats having empty GCDs. And, since it hits 3 times, you have a fairly high chance to proc Infiltration Tactics (if its CD hasn't already been activated).