What the heck happened? Was it my heart?

I was at the store getting some things and all of a sudden the first three fingers on my left hand went numb. It then traveled up my arm, then my left leg went all rubbery. Then i felt my heart in my chest stumble, and skip a beat. Felt like a PVC, ( i get those from time to time ). Then i started to breath heavy. I was alone where i was, so i went out to the front of the store just in case i passed out someone would see me. Then my other arm went numb. It felt like hot pins and needles down both arms and then a strange knotted up feeling deep in my stomach on the left side. I have a blood pulse oximeter. I put it on my finger and it showed my blood oxygen was all the way down to 91%. and my pulse was 115. I had a blood pressure cuff in my car. I got to it and put it on. it showed 158/100. At this point i'm starting to feel worse. So i call 911. But by the time the paramedics show up I'm normal again. Blood oxygen is back up to 97%, blood pressure is back to normal. They hooked me up to their EKG/defib machine and everything looked fine. What the heck happened? A similar incident happened to me about a year ago. I drove myself to the hospital that time. And again, by the time i got there, I was fine again. They found nothing wrong and sent me home. I had a cardiac stress test shortly after. All fine. And here i am a year later doing it all over again. I know yahoo answers isn't a doctor's office. I'm just looking for ideas that might help me figure this thing out. Thanks.