Weigh in Monday’s.

So I went to WW on Mon. an I lost, but not what I was hoping for. .2lbs. Big deal! Well I guess it is better than a gain. I have been at a weight loss plateau for a month now.
Feeling very frustrated about this I exersiced today for 30min. on the treadmill and did the bender ball video. level 1 & 2.
Skip to 6hrs. later…… My abs are screaming. Help Help Help.
I can only think of two reasons. The exercise really works or I am that out of shape.