Please help, pounding every 4 or 5 beats

Dear Forum, I have joined as am full of fear a bit today and it has been comforting to see I'm not the only one with this type of issue. Basically I have had various kinds of palpitations investigated. I saw a specialist a year ago after a very long fluttering that lasted about a minute, he said dont worry
, and was due for a check up a year later but I bought it forward a few weeks as I have had some new sensations and feelings which he confirmed today. Basically I notice when I hold my chest I have 3 or 4 or 5 normal beats and then 2 or 3 pounding ones and this is constant. And they seem to come from a different part of the heart. He has put me on 24 hour tape as he could hear them when he listened. I'm due back for echo next week. I'm scarred because it's always there. I think it's been like this for long time and feels worse now as I'm very stressed and run down. Does anyone else have this regular pounding every 4 or so beats? They are In time but pounding. What does it mean? I'm but scarred so any ideas would be welcomed. Many thanks, Mark