Please take brimock & Raggedy Ann's suggestions above, they're good ones, and for the love of god, please read and digest this information:
http://www.wikihow.com/Use-Apostrophes
You are in college now, you must know when to use an apostrophe to indicate something plural versus something possessive. Your misuse of it is much too frequent to just blithely slough off to being on a forum, one can only assume you really don't know the difference and in many cases, spell check may not catch it for you. These are rules you need to know to function as an adult and eventually, as a professional.