I understand that Zihar is unlawful, and it is something to the effect of calling your wife like your mother in an attempt to divorce her. And this is a little TMI and embarassing, but sometimes I call my wife "Mom/momma/mommy" playfully, both her and I enjoy it. But I was wondering, have I accidentally been doing zihar on her?

Your intention is not dihar, so just these names don’t impact your marriage and so it should be fine