Drug charges on record

I am currently a student at SJRCC in the state of Florida. I have almost completed my pre-requisites for the nursing program and will be applying in the spring for both SJRCC and FSCJ's summer term. I am extremely nervous due to the fact that i have made some very stupid choices in my past. I am currently 23 and have been charged with a misdemeanor of marijuana/paraphernalia 3 times in my past. The first time was in march of 2007, the second in january of 2009, and the third in March 2009, all of which i was given the defferment program where i had community service, fines, and classes to take. When i apply for the program it will have been almost 2 years since the latest incident, and when i finish and sit for the NCLEX it will have been a lil over three and a half. I no longer smoke it, but even still I know your past can haunt you. I am getting very nervous due to the fact that NO ONE can give me any inkling as to whether or not i even have a chance. I understand that each person is reviewed on a case by case basis, but 18 months is just a long time to throw away. I am just curious as to wether or not any of you might have any advice or personnel reference for me.