For roughly three weeks I have been dealing with vertigo low heart rate loss of appetite and extreme exhaustion about a week ago I was told I have fibrocystic breast disease could they be related

Fibrocystic breast disease sounds worse then it is. And your doctor or whoever diagnosed you with this should have explained it further. If I had not run into this with a client already, I could not give an opinion, but already researched the condition. It is lumpy breasts without anything related to cancer if that is what you are thinking. No, the symptoms you describe are not associated with lumpy breasts. I think you need to talk to your doctor about the symptoms you are referring to and quite frankly, I would say they sound like low hormone condition as in menopause although you don't say how old you are.