Im 31yrs old. i started smoking since i was 15. is too late for me to quit smoking for save my health?

No, not too late: Even cutting down or stopping for a period of time makes a difference to your cells. Will they return to their 14 year old condition? Probably not. But never let the perfect become the enemy of the good. Quit as soon, as successfully - or as often - as you can. Since you are pregnant there should be no doubt at all! babies need mothers who don't smoke. Congratulations and best wishes!