Gezinha, I don't know if this would help but here it goes ...
If you went to college or university, you can use your enrollment verification as evidence. It is called National Student Clearinghouse, it is a huge database that consists your info and your degree enrollment/verification.
If you have any type store cards, for example CVS,Safe Way, Giant, rite aid etc ... and you used it to make purchases at any time, you could call the companies corporate office to get your purchase history. I know for fact CVS keeps all its customers purchase history in some type of database because I use to work for them, and we used to tell customers who wants to get reimbursed for their medical related purchases from their health insurance company. If they say no, make sure you insist or ask them to escalate the call to upper managements.
You have lots other options as well. Don't let the RFE discourage you. Good luck