You're right that you're BMI is fine. In fact it's 23.3 which is clearly in the "normal" range.
The best way for you to lose weight is to stay around 1,400 calories with a diet that has lots of fruits, vegetables, cereals and grains along with lean protein and LF diary products.
In addition, you can try to increase the intensity of your exercise; not necessarily the duration. That might help burn more calories.
With your BMI you're definitely not a candidate for Alli.
I hope this helps.
Pat Baird, MA, RD, registered dietitian