I had the same thing start in my 5th week of first Test E cycle,laid awake at night listening for my heart to pound really hard like it would occasionally,would wake me up at night as well,so after a week or so, I went to see my Dr. who is a Cardiologist,Ekg,bloodtests,bloodpressure all normal,he gave me script for a beta blocker,I never took them,but knowing everything was okay with my health,it pretty much went away.At least I stopped thinking about it so much,that helped the most.