MTC you really need to gain some lean muscle then cut body fat. Body Pump will not give muscular bulk. How were you measured for your body fat %? Dexa or Pinch?
Without the lean muscle you will look nothing more than a skinny girl.
A friend of mine recently cut for a comp and didn't bulk enough, she ended up looking like a malnourished skinny girl at about 14% bodyfat. She missed this years comp season. Will post some pics when I get on my laptop.
If you are on a forum asking this question of where to start, you really need a coach. Your current low bodyfat is an advantage.