Slow heart rate despite anxiety? Advise!

For the last 6 months, I have been suffering from frequent palpitations (punchy heart beats that vibrate many other parts of the body). Its accompanied with several other symptoms, notable ones being laboured breathing (difficulty breathing out completely), chest pressure and occasional dizziness. The palpitations are the worst while lying down. In the initial days itself, I got several blood tests, two ecgs, one TMT and one echo done. Everything came out normal except a vitamin D deficiency, and I was told by doctors I have anxiety disorder. I havent taken any medications yet. My resting heart rate is between 55-60, and it never goes too high during these episodes. In fact, I have seen my pulse rate increase and decrease considerably (by about 5-10 bpms) while breathing in and out respectively. Episodes have become worse since, and I am really starting to doubt if it's all just anxiety (I have heard anxiety attacks are accompanied with an elevated heart rate). Please advise!