Getting Scared

So now I am in my 3rd month of taking phentermine.. the very first time I took it I was terrified because of the possible side effects ( heart problems, liver, kidney, etc.) But when nothing happened I began to feel O.K. with it.. Then last month a lady came through my line (I'm a cashier) and told me that she has leakage in her heart caused by phentermine, as told to her by her doctor. Now since I've started having stomach problems and such, i am begining to get scared again. I dont want to quit taking it. I've Lost 23 pounds so far and I'm starting to feel good about myself once more.. But Is it worth it to take something that can possibly kill me when the weight may kill me just as well? I dont know, I dont have the answers and I'm afraid to tell the doctor because I dont want him to take me off of it.. So for now I'll see if my stomach gets better and decide before my next appointment..