That’s pretty common. I didn’t have any G-spot sensitivity until I started combining G-spot play with clit play and that caused me to develop sensitivity in there. I don’t know how it works but it does.
My recommendation for you would be to get a clit vibe and a good G-spot dildo and use ‘em both at the same time. And don’t shame yourself if G-spot play doesn’t do much for you even after that. Not everyone’s super sensitive in there.