Vaginal tissue is very sensitive. Guess he did his homework! Also, if you can't find the G-spot or it doesn't feel good to your partner, giving it a few weeks and then trying again may be to your benefit. Doggy style sex g spot her upper body raised on the bedhead of some pillows can also help.
And this goes doubly if you have found it, and your woman loves it when you hit that spot. With practice, you'll be able to make her climax through g-spot stimulation as easily as you give her a clitoral orgasm.
I tried the curling your finger thing, no dice. So, we've covered all the ways to reach the G-spot with your fingers.