Are your friends bigger than you? It may not make them feel so great if you keep banging on about wanting to be slimmer if they have trouble maintaining their weight themselves.
I think you should go see your GP and make sure that you are not going end up underweight.
However, I was unhappy with my wobbly bits and starting going to Body Pump classes five weeks ago (I only go once a week, although I also do yoga and swimming once a week too) and my body shape has changed dramatically, I now have toned my entire body in such a short space of time and feel really good for it. On the scales I have not lost an ounce but am more toned and stronger and I eat whatever I like, although still have a balanced diet.