When it went up, did they do a confirmation test to see if you have a new infection? It's common for it to stay at the same titer, but I'm not thrilled with it going back up. That needs further investigation.
That is something you should confirm with your doctor, since we do not know the full history and how exactly you were treated.
Normally, if your RPR titer increased some time after treatment following a 4-fold decrease, it probably means you have syphilis. It might be a case of failed treatment (those are not too common but not unheard of) or a new infection.
But the decision should be made by a doctor offline.
You should speak to your doctor about it, re-test, if needed, and get another course of treatment. It would be a good idea to have your wife tested too.
If you still have syphilis, you should first get treated and then plan parenthood. While a single course treatment may occasionally fail, a case of incurable syphilis is impossible. After treatment you will be a happy father!