Officially introduce yourself to the community by sharing your goals, obstacles or accomplishments. Don't be shy.. we're all here for the same reason. The more support we share the easier it will be to reach our goals!
The most FAT you can lose is about 2lbs a week. Any more than this and you are probably burning up muscle. This will slow your metabolism, and cause you to pile the weight back on. So, realistically, the quickest you could lose 15lbs would be about 8 weeks.
If you fill out your profile, we can give more specific advice, but why not get an exercise program and nutrition suggestions from this site?