Does anyone know if this from anxiety?!

I been to doctors had everything done everything blood cat scan xray sonagram echo cardigram done and always was good always in junuary I went to doc get another check up course blood everyhing good did another ekg she comes back and says ur heart fine just had a palpitations here and there extra beat or two but my heart waz always beating fast bc I was nervous ..I told her I had anxiety she sid that mostly wat its from...bc since I was young I never been told I had that so I'm thinking just happen at the time wen I had ekg done that day..I was just wondering is just from my anxiety that day...my anxiety been gettin to my had very bad dizzy I always think I'm dieing even though doctor said my blood work and everything was good. Why can't I just stop thinking that too:I(