Hi there!
My reply to your question is : YES. I have had almost identical symptoms and had identical worries. Let me go over them and I will tell you what I have done.
After a severe shock, I noticed that my heart was beating with funny rythm, and was missing beats, which were very noticeable, just like you. It would happen out of the blue, but usually after an argument or during a stressfull situation, mental or physical.
I visited a cardiologist, who could not find anything wrong after a cardiogram, but fitted me with this 24 hour monitor. He told me to record everyting I was saying or doing when I would feel the beats missing. When he checked this long record I have kept, we found out that it was happening every time I was raising my voice, feeling sad, had stressfull thoughts or was in a difficult situation. Right now I do not remember whether it was also happening when I was doing something physical, but rather that regular exercise was alleviating the problem by relieving my anxiety. After giving me a thorough heart examination including effort test and echo test, he decided it was pure anxiety, in my case. So he gave me some antianxiety medication ( LEXOTANIL) for about 9 months and my situation gratually got better until it DISAPPEARED.
Since then, 8-9 years ago, I sometimes get these flutterings when I go through a stressfull period and I have come to recognize that my stress level is going up when these heart irregularities happen. So I try to defuse the situation by exercise etc.
However, I know that this is causing you more stress by fearing the worst and hence, it is creating a vicious circle. So, I would recommend that you see a specialist and have all the appropriate tests to put your mind at ease. Apparently it is something quite normal. In my case it also happens when I am expecting my period. But then ... I am a woman!!!!
Good luck