Heart attack?! Pleurisy?? Anxiety attacks?

For those of you who may know of pleurisy, I was diagnosed with it at 13 years old. For those who don't know, it's inflammation of the walls between your rib cage and lungs that impairs their lubricating function and causes pain when breathing. It is HORRIBLE! Now I've been to the doctor plenty of times and they don't take me serious since I'm only 16. I get pains in my chest that are unbearable. This happens any time of the day, I can be happy, sad, mad or even just laughing and having a good time and boom. Something sharp hits me and stop everything and I'm unable to move or breathe. I always get scared thinking I'm having a heart attack but I try not to think of any negative thoughts to prevent from any more pain. This sharp pain usually remains more in or under my left boob. Other times it can be lower under my boobs and never more than one sharp pain at once. I always just hold my chest and either rub or pat it just to try and force it away. I've taken ibuprofen for it but it doesn't help at all. Do any of you have the same problem or may know what's wrong with me? How else should I convince my doctor to prescribe some type of medication to help me? I need answers :(