I signed a lease in May 2011, have paid same rent all those months. Owner sells property and new owners want me to sign a new lease with extra forms I don't know about. I said no I'm not comfortable signing nothing extra. What to do?

The lease does not change when there's a new owner unless you agree to the change.

The owner bought the property WITH the terms of your lease. They can either wait until the lease ends OR buy you out.

They cannot change the terms and if they try you are not obligated to agree.

If you signed a lease on May 2011 ( that was 13 months ago)

How long was the lease for ? If it was for one year, it is over and there is no current lease. If there is no current lease, they can demand that their lease be done for a new lease, and if not you are renting on a month to month, and they may evict you.

So, if the May 2011 lease was for over a year, it is still in effect, if it ran out last month May 2012, then now, June 2012, they can demand a new lease or request you to move.

Unless your lease was for more than a year, it expired as Chuck said. So the new owners want you to sign a new lease. That is par for the course. If you don't like the terms of the new lease, give then notice that you will move or negotiate different terms.