Never change your oxygen flowrate unless prescribed by your doctor. Your symptoms may worsen if you use either too much or too little oxygen.
Shortness of breath is not always because of too little oxygen. Such symptoms may be due to a flare-up in your lung condition caused by a cold or chest infection.
If you are experiencing shortness of breath:
Sit in a comfortable position, stay calm and try to control your breathing. Pursed-lip breathing and diaphragmatic breathing will both help. (link) These breathing exercises reduce the trapped air in your lungs, which allows you to breathe in more fresh air.