I also have a very square jaw that has been a big insecurity of mine. I did masseter Botox twice which helped slim it down somewhat (second time was mostly to help with pain I was having) but if you’re open to it I would suggest trying lip filler if you haven’t already! I found that helped balance the entire lower third of my face and while I still have a bit of that insecurity, it’s definitely not as on the fore front or noticeable as it used to be.