It depends what the OP's real goal is...is it to temporarily drop 15-20 pounds, or to reach and maintain a healthy level of weight and fitness over their lifetime?
You could do lots of dumb, unhealthy things to drop weight fast. But if you want to be fit and healthy, it needs to be a lifestyle change.
Only you know how committed you are to it. I'm 30-mumble mumble, weigh 160 and am just shy of 6 ft tall. Have been fit since my early 20's (before that I was thin but didn't exercise on purpose...it just happened). I'd recommend doing several things:
1. Read Covert Bailey's "New Fit or Fat". It's a classic and explains a great deal about how the body works and the importance of both eating healthy and exercising. Sorry...just doing one or the other is not going to be enough for the long-term for a fit body.
2. Get your BMI tested (body mass index). This is better than just knowing your weight because it tells how much fat you have and whether it's a healthy level or too much. I'd talk to your doctor and have them help you set a goal and make a plan. You mentioned you're exercising 3x a week -that's terrific! Depending on what you're doing, it may be building muscle, which weighs more than fat. If someone didn't know that, they might get discouraged and think that the exercise was not helping, but muscle helps burn fat...just read the "Fit or Fat" and it'll explain way more thoroughly.
3. Get rid of the junk food in your house - sodas, sweets, chips, sugary cereal, etc. and make sure you have lots of fresh fruits, vegetables and lean meats.
4. Start checking calories and fat per serving on the foods you eat. You may be surprised. There are tasty ways to eat healthy.
5. Watch your portion control on meals. Check w. your doctor on how many calories you should be taking in each day.
6. Check how many of those calories you may be taking in via liquids - drink a lot of water.
7. Don't skip meals. You'll get too hungry otherwise. Snacking on healthy things like nuts, fruit, yogurt, cheese, etc. is good. I eat about 4-6 times a day (counting B-L-D, a morning snack, usu. a granola bar and fruit and sometimes an evening snack of granola and yogurt, sometimes dessert too!)
8. Don't eat sweets when you're hungry. I LOVE sweets and I eat 'em, but if I'm actually hungry before dessert, I'll fill up with that granola and yogurt and then have the dessert - just a small portion. Otherwise what if I filled up on pie, ice cream, etc. until I wasn't hungry? That's too much fat/sugar.
9. Don't think some fad, gimmick, diet, etc. is going to cut it. I have, however, found that a couple friends have found success with Weight Watchers - if you can handle all the "points"...they have kept weight off long term (years).
I wish you all success - health is a great thing.