Is my heart having a disease if the littlest effort makes me really tired that i can barely breath? and is beating really too fast sometimes

Exercise intolerance: If very slight effort makes your really tired and short of breath, you should wonder if there is a problem with your heart that is making it overloaded with such little activity. The other common cause, however, is simple deconditioning. If you do not exercise regularly, and try to start exercise like a walking program, initially you will feel very short of breath. Take a rest and continue.

Shortness of breath: What you are describing may not be just the heart. The problem could be related to your lungs, blood count, or other disease. It is important to see your doctor as soon as possible so that a full history and physical can be performed to narrow down the possible causes. If you can't speak to your dr right away, then try an urgent care or even er! you never want to ignore heart related problems!