5 weeks PP weight loss.

I know this is overdiscussed but I need some real advise here . In so frustrated that I am not losing any weight . I gained 25 pounds during pregnancy , when I got home I was - 12 pounds . Now I'm 5 weeks PP and not even a pound came off . I have been going to the gym since 3 week losing 600 calories per visit , going at least 3 times a week . I have no appetite at all I eat oatmeal , soup or salad for lunch , and only fruit for dinner , drink lots of water and eat no sugar or carbs . I also breastfeed . Why am I not losing weight ? Every day I get on a scale and want to cry !!!! Anyone had the same experience ? I need to know if this is going to get better , I have to go back to work in a week and I don't want to buy cloths size bigger .