Newbie to MFP- lost 100lbs need to lose more!

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Hello all, I am a newbie to this site- here for a little over a week now. Loving everything about it- the tracking of my foods, work outs, weight and most of all knowing there is support readily available to me whenever I need it.
I lost a little over 100lbs starting from the summer of 2010 and have been trying to maintain this weight loss for the past few months with no real luck. I started gaining again and now my Dr. says I should get down to 140, so that means another 33 lbs for me! I need help, because these last 30 pounds I don't think want to budge!!!!
So thats my story- hope I can reach goal, tone up my sagging body and get into the perfect health so I can stay active for my two little kids!
Thanks for reading,
Christine