When did you start trying to loose weight? Initially, you will loose a fair amount of weight pretty easy during the first 2-3 weeks. Over time things seem to average out closer to what the simple math suggests. There will even be times when you are eating less than your BMR and you will actually gain weight. However, back to your question; to even guess if what your BMR is we would need to know your age, sex, height and weight. While everyone is different it is highly unlikely that your metabolism would be that drastically different.
Also remember there is a difference between BMR and daily caloric needs. BMR only accounts for what your body needs if you do NOTHING. Based on your stated activity level you would need to multiply your BMR by 1.2 to get an estimate for daily calories burned. If you are really interested/concerned you can actually have test run where doctors measure the amount of C02 when you exhale to determine a more accurate BMR.