What Causes Heart Palpitations With Chest Pains?

My heart pounds whenever I move from getting up from laying down or sitting or when I lay down. I can't exercise because everytime I begin to my heart races and pounds. I have anxiety an have had every heart test done. Everything was normal except I had a very slight backflow in one of my valves. My doctor said it was so slight that it won't affect me. I get chest pains an I always feel my heartbeat when I touch my chest and it feels very abnormal sometimes. I have anxiety disorder but am convinced it's not that. Please help I'm only 18 and would like to get rid of this