Anyone else feel like they are blowing it

I'd lost 100 lbs but have gained 12 back these past few months!!  :-0  Yikes!  I notice that I can eat more and enjoy wine.  I have recently started walking again and also have taken up bicycling.  I feel so much better when I do some exerecise; thought I've never been an exercise fanatic (wish I were!).  I need to do better and would like to drop 20 lbs.  I'm at 159 right now.  Was at 147 and felt so much better.  I'm scared!