Need to help getting back on track

I had my 7th baby, a girl, almost 11wks ago. Before I got down to about 130-135 lbs. Not long before I got preg with her I was starting to gain back. Now I'm up to about 170 or so, not sure. I have started dieting and stopped so many times since having her. Just can't seem to get the determination to stick to it :/ I was happy with my 130ish weight and wanna get back there. What helped motivate you to get going strong again?