Heart Issues! It started when I was watching TV.

Ok, it all started when my heart for no apparent reason started going raped. I was watching TV Lying down, I was relax, then my heart started going crazy pumping raped and hard, it lasted about 15-20 minutes I didn't go to the hospital right away until later that night, when I took my pulse, it was at 110. I went to the ER they did an x ray, blood test and an EKJ? (I think that's what it was called), the blood test came out good the x ray came out good the doctor said my heart was very healthy, no clogs, my valves are clean, he said I cannot get a heart attack no matter if I feel like I’m going to pass out or anything he said I have no heart disease. The doctor said that I was very healthy which was surprising because I'm heavy set and I thought that was the reason why my heart was acting up. The doctor said maybe the flap (I recall) didn't developed correctly that it was common in young people in my age, I'm 24, and he recommend me to a specialist. After that my resting heart rate has been 80-90 for a week or two, I try to do exercise but my heart rate goes fast quick and it's uncomfortable. When I slept I would wake up and feel my heart rate go real slow and I would feel wired, sometimes it would be fast when I wake too, I tried to wait it out and see if these conditions would go away but it hasn't. Shortly I have been feeling some minor pains in my arm, the pain mostly feels like pressure, I felt pain in my shoulder, neck and my chest, it comes and goes, never at the same time and never for very long well the arm pain sticks around more. Recently my heart rate has been going slow about 60's then just two days ago it reached 55, so I went to the ER again I was concerned, doctor said I was fine, if I'm not feeling symptoms while it's that low then I'm fine, my blood pressure is good, she said that athletes heart rates are low etc. but I'm not fit so that's sketchy. Now today I’ve been feeling pain under my left breast I guess the rib area I'm not sure if it's in any connection with the heart issues I'm having, But I believe so because I know I didn't hurt myself in any activity, it only hurts in that area with certain movements. I have an appointment for the clinic on Friday then if it's necessary they will appoint me to a specialist. Has this happened to anyone? I’m afraid that I might get a heart attack I also fear my heart will stop because of the low rate, I have been really worried lately and my anxiety has been somewhat high at times, I'm a nervous wreck :-(