Photocopies of pages 1 and 3 of all I-20s issued to you since you first entered in F-1 status, including the I-20 issued with the OPT recommendations. Do Not Send the Originals of any I-20. Be sure you have SIGNED AND DATED all your I-20s on page 1. Note: The USCIS wants to see all your I-20s starting from the one marked "initial attendance". If you do not have all your I-20s and are unable to obtain copies from the appropriate school, you should attach a brief explanation of your F-1 status history.

 can I contact my previous college and ask for a copy my previous I-20. Do you guys have any idea about that??? 

You need to have all the I20s. That means any I20s issued since you were a student. I don't think your college keep a backup. They just print and give it to you. So, your best bet is to contact USCIS and ask them instead. They must have some way out of it.  If you miss one I20, then your OPT is rejected. It happened to my roommate. So, you better be cautious and apply once you are 100% sure about the documents.

If you are applying for OPT ... usually the current university you are enrolled in right now.. will do it for you. In my case, my university applied for it before I gradated from there. 
I havne't heard anybody applying it themselve but I've done the OPT- exntension myself for 17 months after I finished my 1 year OPT. All I needed was the I-20 from the university I graduated from...they will issue you one when you ask them.

btw I was enrolled in community college as well.. I had lost the I-20 from community college... I didnt need to have it anyway.

so My suggestion is, just ask the current university and tell them you are filing for OPT, they will issue you with new I-20 that will state that you are applying for POST GRAUDATION OPT. You just need that one.... no need to gather all the I-20s.

hope it helps.

Thanx