Anxiety and terrible feelings in my body

Around three months ago, I was driving and started feeling dizzy and after a while i started feeling like i was out of my body, then i would start having palpitations and weakness all over my body. on one occassion i had serious palpitations, my heart was throbbing throgh my chest, tinglings in my arms and feet, and my tongue was stiff, I could not talk, I was then taken to the hospital and I relaxed and all the symptms calmed down. My doctor told me it was mere anxiety and gave me some drugs. I took the drugs once and a week after that i still kept feeling dizzy all the time, tightness in my chest and stomach, weakness in my legs and arms. I thought it was a heart condition so i went to see a cardiologist and conducted an ECG and Echo but found nothing. I went to see a cardiologist who then gave me only B12. Up till this moment i feel weak when i wake up in the morning even after sleeping for about 8 hours. I still feel weakness in my body and dizzy constantly.Im not on any medications right now. i stopped taking every thing for over a 2 months now but the weakness in my legs gets better when i do exercise, someone please help, i am scared that it might be something more serious.