What Causes Heart Palpitations,extreme Fatigue And Severe Insomnia?

I've been having heart palpitations, extreme fatigue, severe insomnia, loss of appetite, severe anxiety.... I recently had a physical and my hormones checked. I was very low on vitamin d but am taking D pills. Hormones are fine. My triglycerides were at 598 but Dr figured out it was due to an antidepressant I was taking which I've since discontinued. I've had no heart checked.. No one is able to find what's wrong... What can I do now? Feel like I'm going to lose my mind.