I agree with Donny. I don't think it's your breathing that's your problem right now, I think that you need to work more on your anaerobic endurance. Don't worry about your breathing technique right now. What you need to do is work on developing your anaerobic system by doing interval training and sparring. Once you have your conditioning up to where it should be, then you can think a bit about your breathing technique. Start off working on breathing while you are on the heavy bag and then bring it over into the sparring ring.