First time mum and need to lose weight!

Hi everyone!
I had my son 20 weeks ago now. I put on 1.5 stone in pregnancy and lost it all within the first few weeks of him being born, went down to 15 stone. I now weigh 17! I guess I just ate chocolate to keep me going! My natural weight is 11.5-12 stone so I have 5 stone to lose! Would really love to get motivated with other lovely mummies!!