Working Out Bad for My Heart?

I feel terrible at the moment. I am unable to sleep, and for the past few days, my heart has been pounding and I have been unable to pinpoint why. I thought it might be due to low calcium in my body because my nails have been breaking as well, but only my fingernails have been showing signs of breakage, and I'm wondering if it's just wear and tear taking it's toll and not low calcium. The feeling of my heart pounding is really worrisome as I've never experienced a feeling like it that's lasted for so long. It's also keeping me from sleeping. I just feel really terrible right now and it worries me. I will stop the working out. I had previously tried and quit a workout schedule because it was causing inflammation in my ribs. Now with this elevated heart rate, it just seems that even a gentle workout won't do. I guess I will turn to walking as my exercise. That will be harder to be consistent with. I'll see if I can start walking for 20 minutes a day.