I can almost always feel my heartbeat in my throat

First of all I'm 21 and this has been happening since January. I suddenly had this episode of a rapid heartbeat and after that I have been feeling my heartbeat in my throat almost most of the time and I can feel it more if I exercise or after I eat. Also I kept experiencing the episodes of rapid heartbeat (palpitations)... which were really scary. I notice Stress can trigger an episode too. So i went to the doctor... I have had a bunch of EKGs all come out normal.. when I have had these episodes during an EKG it shows Sinus tachycardia. I had an Echo-cardiogram, which also came out completely normal. Got checked for thyroid... also normal. General blood test also shows everything normal. So I don't have no Anemia either... so the doctor said it was anxiety.. which I sometimes start to doubt. I was prescribed a beta blocker which lowered my heart rate.. but doesn't really do anything for the sensation of my heartbeat in my throat. I can even have a pulse of 70 and still feel it. Can somebody tell me why is this?? & will I have to live for the rest of my life with it? It's really annoying. I really don't know what to do... I keep praying time would make it go away but it's still there for all these 6 months... :(