Got EAD card but did not graduate as planned. Help~!

[IVPhan]

Hi guys! I have a question regarding my F1 status. I started to apply my 12 month OPT on Feb last year and decided to begin my OPT on May, 13, 2014, just one day after my original graduation date. I got my EAD card on April. However, after receiving my card, I decided to delay my graduation because of my thesis. I told my school to extend my program to August. But I forgot to tell my ISSS to extend my I-20 in time. Later I told this to my ISSS advisor but he said I could start my OPT as pre-graduation OPT and I could do post-graduation OPT after I graduated. But I'm still worried about my F1 status since I didn't tell ISSS to extend my I-20. Some said that no change can be made since I have already got my EAD card. And EAD card cannot be cancelled...
Really worried about this. Anybody help?
Thanks!