First, I am going to give you a little anatomy lesson. There are two major types of bodily pain: visceral and somatic.
Visceral pain comes from the internal organs, including the heart. It is an odd kind of pain--very difficult to localize precisely because of the way the nervous system is wired. You literally cannot put your finger on where it hurts. It has a deep, strange, often nauseating quality, and nothing you can do in the way of body positioning changes it.
Somatic pain comes from everything outside the body cavity, like the muscles on the outside, such as the shoulders, neck, back, and hips. You *can* put your finger on it. That is, you can touch it, and changes in body position, for example, can make it better or worse. So can massage, stretching, or hot and cold therapy.
Because of the way the nervous system develops in a baby, there is no overlap between these two types of pain.
In a nutshell, your description of your pain is entirely somatic. Nothing you describe is related to your heart, for cardiac pain is not touchable on your body's surface. Cardiac pain is not associated with muscular spasms in your arms or chest or shoulders. This is a fact that you simply must accept.
So what is wrong? 1. You are clearly suffering from anxiety. Zoloft is often quite a good drug for panic and anxiety, but when it comes to anxiety meds, one size does not fit all. I believe you should have another talk with your prescriber (and I hope you are seeing a real shrink for this rather than a GP, since this is a specialty area) and ask for a trial of another medication. One important fact: You have to take any psych medication faithfully for one full month to see the true effect.
A combination of anti anxiety medications and something called cognitive-behavioral therapy can often be more effective than either meds or shrinkage alone.
2. Please google 'Da Costa's syndrome' and 'cardiac neurosis.' When people have anxiety that is improperly treated, they often kind of seize on heart disorders as the cause of their pain, even though their hearts are fine.
3. It wouldn't hurt to investigate the possibility of fibromyalgia. This is a real and very painful disorder, more common in women than in men. You can google it. I have it, and finding the right treatment can take a bit of time. A rheumatologist is the right specialist to see for this, and believe me, relief is possible. A key element in treatment is medication that gives you a good night's sleep.
4. However, your fixation on your heart is a separate problem. You will not be able to get over it without intensive help from a good psychiatrist. Please find one and follow his or her advice.
Good luck to you.