Could his previous addiction to marijuana be preventing us from concieving a baby?

My significant other was formerly addicted to marijuana. He is clean now, however we have been having sex without any form of birth control for about a year and 6 months and im still waiting on the positive pregnancy test. Could his marijuana use be the reason?

: http://alcoholdrugstreatment.info/could-his-previous-addiction-to-marijuana-be-preventing-us-from-concieving-a-baby