Chronic Fluttering. ECG Showed Fast Heart Beat. Can I Have Bowel Cancer? What To Do?

I am 47 almost 48, male with no history of depression (but it is in my family); and no familial history of heart disease as such (though my father had right branch bundle block and a mild heart attack at 62, likely from clinical depression, chronic heavy smoking; and severe alcoholism ). My issue, is that I have a chronic fluttering /vibration which is quite aggressive in my chest. It developed slowly over the past seven years and it is worst when i sleep. I wake up several times a night (4 or 5) with a flutter, which sometimes becomes a faster heartbeat . I do not know if the source is cardiac although i had an echo last october which showed my heart is structurally normal (although left atrium is 4 inches and was 3.5 inches in 2005). I have a mild mitral and tricuspid leaks. I was taking part in some activities in 2005 which may have perforated my colon , though i do not think anything untoward happened. I notice that the vibration is heavy and gets worse (constant), before i have to poop; then it subsides. At night, when i wake up (this has been going on for about six months), i have a palpable pulsation in my left chest. Using a portable ECG, this has on two ocassions shown suspected fast heartbeat; other times, wven though the pulsation is quite palpable, there is only a normal wave form on the ECG. I also get quite tired around 2-3 pm and feel exhausted; and in 2011 i was diagnosed with moderate sleep apnea (it was not made clear to me whether it was OSA or CSA but i had very bad CSA at the time and this has now resolved a lot, so i only have a few apneas that i know of, as i do not use the CPAP all the time now). I do not think sleep apnea is causing the current pulsation which is severe just before pooping; in the past, i used to get very severe abdominal cramps before pooping, to the point where it felt like i was being stabbed. Now that these cramps do not happen, instead, i get the pulsation. Is there any doctor out there who can help me? I have pretty much given up hope of finding the cause. I suspect a twisted or perforated bowel; bowel cancer (my Mom died from bowel cancer last year); or a congenital cardiac complication which is hidden on a stress echo but which is significant enough to cause heart flutter at night or the vibration is coming from a large artery which may have an aneurysm. None of the doctors i have seen (i have seen 25) are willing to or interested in doing further tests to find the cause.