Three things come to mind. It seems weird though and I would recommend going to a doctor which could help you if there's anything physically wrong. Don't write

Three things come to mind. It seems weird though and I would recommend going to a doctor which could help you if there's anything physically wrong. Don't write it off, standing and singing should not be a problem. Asthma? There is a trick where you put your index finger on your fore head and thumb and middle finger on each side of the nose. Start by closing the lefy nostril and take a deep breath with the right one. Close the right nostril as well and hold, open the left nostril and breath out. Both inhale and exhale should be slow. Do an easy task that need some thought and try to talk at the same time, try some different combinations. I can't talk if I do something that takes any form thought. It just could br hard and you need to practice, or you are just incapable and need to work around it instead.