PVC's and lightheadedness

I had a heart attack (lower part of heart) in July 07 which resulted in 2 stents being put in. Since the heart attack I get a lightheaded sensation in my head followed by a single strong heart beat (PVC's?) (did not cause dizziness). This happens in less then a second. Also I now have great difficulty working close to the ground (shortness of breath when squatting and doing work close to ground level). Three months ago, started getting light headed when these sensations occur as well as them occurring much more frequent and now I have palpitations (can feel the heart beating (never could before the last three months). Now I am slightly lightheaded for long periods and when I get these sensations during periods of lightheadness I really get dizzy for a quick moment. Very concerning when driving. Last week I did a stress test where they injected something during the test. Blood pressure went from 90 over something to 100 over something then back to 90 during stress test. Went in ER last week with mild chest discomfort. After heart cath ( no findings, unstable angina ) I was released. Are these sensations PVC's? Should I be concerned since I have had a heart attack? What about the dizziness and shortness of breath when working low? Are these of concern or are they even related to the heart attack? ( 50 years old, 5'5", 160 lbs). Thanks for any help or direction to finding info.