Why am I not loosing weight quicker?

2lbs/week seems about right from the numbers you've posted (if not slightly higher than expected). Bit of maths for you:

3500cal = 1lb
based on your size and weight you probably need around 2000cal/day to maintain before exercise
5 classes at ~500 cal a class = 2500cal/week
deficit through diet =~500cal/day = 3500cal/week
Total loss/week = ~6000cal = ~1.7lbs

Due to a few estimations we can easily take in to account the 0.3lb difference. A lot of people get a little downhearted at the idea 3500 calories is only 1lb lost, but just find something in you cupboard that weighs this much and you'll see it is significant (and you are losing 2 of these). You're doing great!

Another thing to keep in mind is that as you lose weight, your weight loss should slow down gradually. You'll also need to re-evaluate your calorie limit from time to time because as you lose weight, you need less calories, so your old target will inch into maintenance instead of weight loss. I did mine every 10lbs or so that I lost, I don't know if that's the norm or not, but that worked for me.