Landlord asks for 2 last months payments?

If you're still living there, then you haven't had your "last month" yet. The "last month's rent deposit" is used when you leave without proper notice, haven't paid and cannot be found. Why would a landlord want to forfeit a month's worth of rent simply because you cannot be bothered to pay?

Under your state laws on security deposits, you will get a full refund of that "last month's rent" only AFTER you vacate, assuming you didn't leave any other unpaid debts or damages.

Yes, it is right. Be grateful that you were not charged a late fee. You have to pay for every month you are there. Any over payment, portion of security deposit, last month 's rent will be returned according to state law.

You prepay the last month's rent as security in case you default. You are to pay the last month's rent as a usual rent payment as you agreed to in your lease. At the end of your lease term your security deposit, less damages, is returned to you.

Yes you were right to have paid. Here's an excerpt from one of the links below:

"Unless the rental agreement states otherwise (i.e. the rental agreement stipulates that you specifically paid upfront for last month's rent), you cannot unilaterally substitute the deposit for the last month's rent. In such case you can only use your deposit as last month's rent if a landlord explicitly agrees to substitute the deposit for last month's rent."

After JDIMWIT:

"...I paid 1st, last and security deposit..." I'd wager the tenant is as confused as you are and they paid first month's rent and a security deposit of X + last month's rent. Or feel free to post a link supporting your position. It would be a terrific change of pace for you.

Did you give your proper written noticee of vacating? If not, you owe this month's rent & your last month that you prepaid will be applied to August's rent that you now owe.

Why didn't you ask him questions? Perhaps you didn't go through the right channels and he didn't know it was your last month. Or maybe he forgot/didn't realize it. You need to be asking him these questions. We can't help you.

it's NOT your last month if you are staying, so you pay

Not correct, Remind him you paid last month when you moved in.