panic attacks and heart thumping

So recently I had a panic episode. Often times when I lay down at night on the couch to watch a little TV or right before I fall asleep at night, just minding my own business and then I get a heart Thump! (up to 3 times ina row) it feels like a half-filled water balloon is being shaken up. It usually happens just once, but it's usually sufficient to freak me out! In correlation to that I recently had a panic episode, where my heart started beating rapidly after drinking some alcohol and it freaked me out... I ended up in the ER all night because I was so terrified of having heart problems or a heart attack. Of course I realize now that I have acute panic attacks from anxiety and major stress.

I just want to know if the single heart thump once every 2 weeks or so is normal and ok. They've done several EKG's and found nothing, I wore a halter and normal, I had an Echo Cardiogram and they said things look ok and I'm scheduled for a treadmill in a couple of days.

I used to drink coffee like it was water and I'm under a lot of stress starting a new business as well as I smoke about 3/4 a pack of cigarettes a day. I have since cut back on the coffee to one cup in the morning, taken a week off after my panic attack, but I'm still chuggin' on the cigs because the doctor told me not to try and quit just yet because I'm only going to make things harder on myself (She said wait until your anxiety comes down). I'm a 25 yr old male.

Any response would be a big help for calming my nerves!