So depressed!

My LO is 7 weeks old & I cannot for the life of me loose this weight! I gained 15kgs when pregnant & have only lost 6, Bub was born 3kgs, to start with up until 2 weeks old we were eating take out as most new moms would adjust to the life of everything! But we have been cooking majority of our meals since then other than take out here or there, I still have 9kgs to loose & I just cannot do it! I'm starting to feel super depressed over this :(