Is my body rebelling?

Today was the weigh in day for me. In the past week, I averaged 1640 calories a day and I made a conscious effort to get out and walk on 3 separate occasions. There were really good days (calorie-wise 1012) and there were bad days (when I ate an entire bag of almond M&Ms -- a whopping 1470 calories). Overall, I wasn't terribly dissatisfied with myself.

I had always heard that if you multiplied your body weight by 10, that is the amount of calories that you have to ingest in order to maintain that body weight. For me, that would be 1930 calories per day. I didn't sacrifice as much as I could have but I still did take in nearly 300 calories less each day than I had assumed that I was taking in before. Instead of eating whatever I wanted, I ate healthier choices. It wasn't that big of a deal to trade in a hamburger for a turkey sandwich. The one thing that I did not do until today was increase my water intake but all in all, I expected that I would go down and weigh myself and find that I had lost a pound, maybe two if I was lucky.

I guess you can imagine my surprise when I weighed in 4 pounds heavier since the last weigh in. I don't know what I would have done had there not been another person nearby, I was torn between crying and cursing. While I don't know what my options are right now, the one thing is sure, I'm not ready to throw in the towel yet. While I know that the definition of insanity is doing the same thing over and over and expecting a different result, I can hardly believe that if I take in more calories that I will lose weight. I think that rather than getting depressed, I need to continue to monitor what I put in my mouth, increase my water intake and get used to exercising every day. I will let you know next Monday how it goes.

Average Calories -- 1640 per day.
Exercise -- 3 times in the past 10 days. Approximately 10 miles walking.