Are Palpitations Due To Anxiety And Panic Attacks?

Back in December (2015), I went off my prescription Prestiq and Qsymia that same week. I went off my Qsymia because two weeks prior, I had feelings of increased heart palpitations that didn t raise too much of an eyebrow for me but still, somewhat of a concern (the Prestiq I had planned to go off with my doctor s consent anyway). The first part of January (this year) the heart palpitations/fluttering continued to get stronger, gradually with each time it happened (back in December, they were sporadic, maybe 3-4 times a day, in first part of January, 15 times a day). I made an appointment with my doctor back in December already for a date mid January and thought that would be okay. Around Jan. 7th, I was driving on the freeway and my heart started to feel like it was coming out of my shirt, then stop quickly. This would only last a couple of seconds each time, but almost would happen every three minutes. It became so bad that when it happened, it caught my breath (still does when it s a severe). I made it back home, went to the ER, and the EKG s, blood work all showed normal results (CBC, thyroid, hormone levels, etc.)...I went to see my GP the next day and was supposed to put me on a heart monitor for 24 hrs. but forgot.?(I didn t receive it) but gave me Propanlol in case the attacks came back. The episodes have continued since but very small until today. Today, the attack was horrible and I almost threw up. What is going on with me? Could this be a rush of adrenaline or would that have caught this in the blood work? Can panic attacks be this severe and frequent???