We do not now know that, because we were not there at every instance that He addressed His mother, nor has every instance of Him addressing His mother during His ministry been recorded. In other words, you may call your mother one name during your private moments with her, and something else entirely in a public situation. All cultures have instances of that.
We are going by what the scriptures say.
Christ made it very clear that His relationship with His family had changed when He stated that all of those who follow Him were equal to a relationship to His own family, including His own mother. (Mk.3:34-35)