What’s wrong with my saw?

After a couple of years of Pilates I still really struggle to sit straight up with legs out. It makes doing the saw etc very hard for me. The discomfort seems to be from deep in the inguinal region anteriorly is this still a hip flexor problem after all this time? It also affects me doing leg circles as you can imagine, I can’t really hold my legs at 90 degree Any hints on what I need to do to sort this out would be most welcome as I am now finding this very frustrating to see so little progress. Thanks