anxiety or heart problems? please help

Hi, i am a 28 year old female. no prior heart problems and no known heart problems in immediate family. on august 29th i had what i believe to be a panic attack. during the attack i called 911 and they did an ekg and said everything was fine and it was not my heart. since then i have had 2 more ekgs, a chest and back x-ray,an ultrasound, and 2 sets of bloodwork. 3 drs. have also listened to my heart. everything has been normal and my blood pressure has always been normal. However, i still have the chest discomfort and sometimes the shortness of breath, although, the shortness of breath feeling seems to not be there if i am not paying attention to my breathing. when i think about it i get sweaty and nervous feeling. if i start to panic, after i calm down some i get cold tremors and jerky. i can be feeling fine and then all of a sudden i get this butterflies in the stomach feeling which seems to be a sign of an attack. also i smoke about a pack and a half of cigarettes a day, sometimes less, and i have a few drinks occasionally. i don't do drugs and i don't take any medications. i even have a reluctance to taking pills that the doctor has prescribed.(scared of the side effects). do you think this is cause to worry about my heart or just anxiety. please help, i feel like i am going crazy.

Thank you so much for answering me. How can I get the pain in my left side to go away. it's just a dull ache and when i'm not paying attention it doesn't seem to be there but when i feel it that is what triggers the anxiety. the symptoms are just so close to that of a heart attack that it scares me. however so far i have not had any severe pain. if it was a heart problem wouldn't something have happened by now? it has been almost 5 months since this all started. also in the past 2 days i seem to have an ache in my cheekbone on my left side but i also have a cold and sore throat, could the pain be from the cold? the first panic attack i had, i called 911 and they hooked me up to the ekg thing from the ambulance and said my heart was fine so i didn't go to the doctor at that time. an ekg would definitely pick up a problem if they did it while i was having the shortness of breath and chest tightness if there was anything there to find, right?