If you are unable to breathe in a dream, then ask yourself how you might be “holding your breath” in waking life. In other words, is there something you are waiting for that might not happen?
Not being able to breathe in a dream may also mean that you are feeling suffocated in waking life. Perhaps there is too much going on, too many issues or too many responsibilities that you have no room to breath. You should also ask yourself if you are in a relationship that is suffocating you.