Drugs are not the best idea. The effective ones are uppers that can turn you into a nervous wreck. If your diet is healthy just cut back on everything across-the-board. If you drink sodas and bottled fruit juices, cut them out. Make sure you sleep enough. If you don't it will be harder to lose weight. Exercise, but not when you are tired.
I don't recommend drugs for weight loss because they aren't something that you can sustain for any length of time. Just like diets, such as Atkins and many others that severely limit your foods; you may lose weight but as soon as you go off it, you gain back.
It's best to incorporate an eating/exercise plan that you can stick with over the long term.
Have you had your thyroid checked to make sure it is functioning properly? Hypothyroidism can cause sudden weight gain, which can seem impossible to get off.