I just graduated and want to pursue another master's degree. My old I-20 terminated on 5/6/2013, so my grace period ended on 7/5/2013. My new I-20 is issued, but it will not be valid until 9/3/2013. My F-1 visa is valid until 7/31/2013. So my question is: have I overstayed in US? If yes, what problems I will meet in the future, and what can I do about it? Thank you!