Why are my upper teeth no longer centered in my face after Invisalign? Should I let my dentist try a 3rd time or see an ortho?

After 20 weeks of wearing Invisalign, I pointed out to my dentist, not an orthodontist, that my 2 front teeth were no longer lined up in the center of my mouth. After another 10 trays, the deviation to the left has increased so it is not centered in my face. He wants to have me wear 19 more trays and tells me they can only be moved 1/4 tooth width. I don't know if that is enough. Before we started, my front teeth were centered but my canines, right more than left, were turned and overlapped.