Its sad to know what ever you are going through. But from the information that is provided, i guess you would be having a condition more to do with your heart rather than anything. Also i can understand that you are anxious which is normal with palpitations, fatigue
and weight gain. I think about weigh gain, it may be just due to a probable sedentary lifestyle with the fatigue factor. Or it needs to be investigated for any other possible causes. But, review with your cardiologist and then for the anxiety
component please request your cardiologist to liaise with a psychiatrist
Thank you and wish you a healthy life.