Help! Need Advice!

I've set my daily goal calories at 1700, per the nutritionist's recommendation. I sometimes eat my excercise calories back. I'm doing strength training and cardio 4-5 days a week (elliptical, treadmill, stairclimber). I've lost 87 lbs. so far and have been hovering around 318-320 for a few weeks now. I know some of it was not sticking to a clean diet for a few days, but for the most part I've been pretty consistent. I have my diary open and would welcome any advice. I'm thinking of mixing up the cardio to incorporate a class with higher intensity (cardio bootcamp or zumba). I've heard of some people zigzagging their calorie goals, and that sometimes you need to "shock" your system by mixing up excercise too. Thoughts on this? Thanks for taking a look!