I want my 20 year old body back

Tomorrow will be the first day of my new diet regime. I am only 20 years old and I am so self concious of my post-baby body. The birth of my daughter stretched my body to no end. I'm not so much concerned about my weight as tightening up my body and becoming a better, healthier me. I feel like if I make the step to change my habbits I will feel better and have more energy to keep up with my 17 month old.
I work with a bunch of super fit women who attend hellish sounding bootcamps, where the instructor makes them drag tires in the sweltering heat. That to me sounds horrible. I am hoping to find a balance, I dont so much want to be a health/workout fanatic but to more seemlessly integrate it into my life. The trick is finding the time in my busy schedual, its so much easier to get fast food for lunch than preparing something. And relaxing on the couch or sleeping in that extra 45 min in the morning sure sounds alot better than running or doing some yoga. Does the motivation come with practice? I guess I'll see.
Time to get serious. Wish me luck
-BusyYoungMother