I want my old body back!!!

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I have recently had a baby (02/14/2012) and am looking to get my old body back. Let me back up a bit. I first gave birth at the age of 17 and, if memory serves me right, it didn't take long to lose the weight. I was even smaller than before I got pregnant. :)

Before getting pregnant this time, I will admit I was a little underweight and could have used a couple more pounds. However, I feel like I will never be the same size again. I realize I am older and my body has changed in the last 12 years. I really do not like myself right now. I don't feel like myself and am beginning to get depressed about my body. I mean, I HATE shopping now and have never worn the sizes I am buying now. While I was smaller before I was pregnant, I did not eat healthy but it didn't seem to matter, I would never gain weight. I feel a little lost because I never had to exercise and don't know where to begin.

Will I ever be able to be like I was before? Any tips on getting started? How long am I looking at? Thanks in advance for any and all responses.