What if I smoke in front of my 9-month-old?

Don't. You are increasing the chance of your child having multiple respiratory illnesses, including asthma, sinus infections, cold, and cough. You are also making it more likely that your child, when older (even in very early teens) will smoke. Quit for the sake of both your health and your children's, or at least have the responsibility to smoke outside and not expose them to second hand smoke.
Quit. If you smoke, set a quit date and stop. Ask your healthcare provider for help in quitting. If you cannot quit, do not smoke in the house or near children.