Sorry, have no idea what the prospects are, but whatever happens, I urge you not to consider "not mentioning it". You are legally required to declare it during the medical, and failure to do so/later discovery of same could land you in deep doo-doos.
I don't imagine a history of drug use would necessarily disqualify a candidate, (it might), but for your own protection (not to mention that of any passengers you may be responsible for in the future) it needs to be declared. Maybe not to a future employer - each will no doubt have rules regarding this - but definitely to the medical/regulatory authorities.