Yes, the mortgage form 1098 will only state "taxes paid" but they are your real estate/property taxes paid.
You would have to amend each prior year for which you paid but did not claim your property taxes. If you itemized your deductions those past years, you may actually get a small refund. If not, claiming real estate taxes will not affect your tax returns.
Here is a link on amending:
https://ttlc.intuit.com/replies/3288565
