Upping calories to BMR - need some advice!

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Hey fellow MFP members, I hope some of you can help me out.

I'm currently 20 years old, 5"10, and 166.8 pounds. My goal weight is somewhere around 145/150 pounds (or whatever I feel comfortable with by then).

MFP gives me a 1200 calorie goal. I've been exercising regularly and eating healthy for a little over a month now. (I sometimes go a little under or over my goal). I lost 3 pounds (of water weight I think) in the first week, but for the last 3 weeks I have not lost any weight.

I'm getting the feeling that my body just doesn't agree with 1200 calories a day. I also read that you should never eat below your BMR (which is 1603 for me).

I was planning on upping my calories to something like 1400, but after reading about the BMR thing, I got a little confused.

Does anyone know more about this? And could someone give me some advice on what my calorie goal should be?