well, it is true the consulate officer approved your visa early because you applied early. but i think at the port of entry you will have problems as they will ask you why coming so early since your program start date is 3 months from your intended date of entry. a friend of mine was send back at the U.S port of entry to go and come atleast 1 month before. By this you can claim you want to get used with the environment and try to adapt before school starts. but 3 months,,, i doubt but try though