Just a consideration, gg depth ranges from 3.5" - 5" avg. = 4.25" so you may not be alone.
Depending how it's measured, I'm 4.25" hey... am I normal?!
I think sex should work fine --- so long you have some 'give' when bottoming out AND NO PAIN!
If your dilator gets to the end, do you feel a FIRM stop, as like in having reach a firm dead-end?
If so it be your peritoneal reflection, part of your pelvic bone.
If so, there is nomore depth to be had, unless you cut right into your abdominal (peritoneal) cavity. This is the case when you have colovaginoplasty.
With inversion, it is an option to do that, only with some surgeon.
Lastly, if you'd have regular sex it WILL get some deeper after a while - IF no pain is involved.
I hope this will help some...