Finding weight loss impossible

Hi. I am new to this site but have been seriously trying to lose weight since January of this year. I started my local gym, going three times a week. The instructor gives me a gym program based on attending three times a week. Each session involves about 25mins cardio and about 60mins of free weights,stability ball, crunches etc. The program gets changed every six weeks. He knows that my main reason for joining the gym was weight loss (I have about 3stone to lose) and has designed the program based on that. He has also given me loads of nutrition advice on good food- egss, vegetables protein cutting out bread etc- which I have been following really well. However the scales have barely shifted since I started in January- about 10lbs in 6months!!! I can't understand this at all, nor can the instructor, as I have been eating and exercising really well and a billion times better than what I was at last year. I have lost about 4inches from my tummy and inches form my arms and legs but still nowhere near what I would have expected by now. With this much weight to lose, should it not be coming off much quicker? I started here about a week ago, I'm on 1230 calories per day, I eat most of the extra calories earned through exercise, although not all as I am aware the calories burned from exercise can be exaggerated. I eat really healthy, allowing myself a few beers at the weekend or else a few snacks if I stay in. After finishing the first week of logging, I have gained 3lbs!!!!! It is so discouraging to be working this hard for so long and to be getting nothing back. I drink heaps and heaps of water a day, prepare all my meals fresh myself and am working my butt off at the gym, what else can I do or is it time to see a GP?