If I filed for divorce back in 1989 and never received paperwork from the court or heard from my ex-spouse, can I be considered legally divorced?

Go to the courthouse where you filed for divorce and get a copy of your case file. You need to make sure there was a Notice of Entry of Judgment filed. If that form wasn't done, it needs to be done and you will need to file for a hearing to request the court enter the judgement nunc pro tunc.

You should check with the court to see if a Judgment was ever entered. If not, then you are not divorced.