Doing It Right - and Gaining - Help!

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I've been on MFP for about 5months, up until recently with great success. I lost 15 lbs in a reasonable amount of time (about 4 months). I had foot surgery 3 weeks ago and promptly gained 4 lbs in a week. My previously very active level went to sitting on the couch and as I felt sorry for myself I ate and ate. Got a grip and went back to working out and watching my calories again. My workouts are not as vigorous as before surgery - I can't run yet so I have compensated by reducing my calories by 200 a day. I even gave up chocolate, cake and cookies for Lent. Well after 10 days of this, I have GAINED another 1.5 lbs. My previous 15 lb weight loss is now under 10. I am so discouraged and so upset. All that hard work to lose the weight seems to be for nothing and there seems to be nothing I can do. Please help.