I actually lost a good deal of weight using phentermine and have kept it off (I'm also 41). I had completely lost all sustaining motivation and it enabled me to find that again and get back into truly eating healthy, not eating any junk and exercising until that was my lifestyle when I quit taking it and I didn't want to stop. I recommend it if nothing else has or is working for you AND it's administered under a real doctor's care who monitors your blood pressure, heart activity and does a complete medical background history. It can be very dangerous if you have ANY blood pressure or seizure issues as well as a few other things. Some info you read says it's addictive, but I never experienced any addictiveness to it or withdrawals from it. It completely knocked my appetite out! I ate, but only when I was truly hungry and it killed all desire for heavy carbs and sweets. The doctor I saw also had me meet several times with a nutritionist. After stopping it, I was "trained" and have had no problems keeping up the correct eating and exercise plan. Good luck!
My opinion on HCG is to stay away from it. I was hesitant enough about the phentermine, but the whole 500 calorie a day thing combined with hormones is just too much in my opinion.