Please dont criticize

I have an honest question of concern and i plan to work everything out when i find out the answer please no mean comments. I smoke weed and spice me and my fiancé plan on trying to have a baby but i want to quit and get clean to have everything out of my system when me and my fiancé start to try an conceive which will not be til May of 2017 i was wondering if anyone knows exactly how long it would take to clean ur system to be able to carrying a pregnancy through without any harm to the child