I've forgotten how to breathe. stress or recent pneumonia has caused me to develop hyperventilation syndrome/over breathing. how do i fix this?

Hyperventilation?: I don't believe you can forget how to breath. If you can't catch your breath we call that sob, shortness if breath. There should be a reason. Before you assume it is stress or anxiety you most make sure it is not from the lungs or your heart. You may need asthma like bronchodilators. Or you may have fluid overload. Have you been back to the doctor? Do you smoke. Have you been told you have copd.

Try Yoga: I suggest signing up for some yoga classes. This will teach you to breath, will improve your health and you'll meet some people that give you support.