Marie - welcome to 3FC!
I think it would be much better to switch to a new doctor in your HMO than to self-treat yourself with any kind of medication.
There might be good health reasons why your doctor doesn't want you to take those meds - only he/she knows your health history. I've also read that frequently the meds sold over the Internet are counterfeit, so you'd be wasting your money and possibly endangering your health (who knows what's in them?)
Believe me, I know the helpless and hopeless feeling of being 100 pounds overweight! My good friend Karen (MrsJim), who posted before you on this thread, says that having to lose 100+ pounds is like me handing you a cup and a teaspoon and telling you to move a mountain. It's overwhelming and seems impossible! But Karen and I and so many people here can tell you - it IS possible to lose 100 pounds without surgery or drugs. One day at a time, one spoonful of that mountain at a time, and you'll get there.
Poke around the different forums here and feel free to jump into one that suits you. I think you'll find a whole lot of incredibly motivated and kind people here to offer you all the support and encouragement you need to lose those 100 pounds.
We're glad you're here!