NO, this is HURTING you! Don't feel that "confusing sharp pains" is actually pleasure. What your boyfriend is doing is hitting your cervix (which is painful!). Tell him not to go so deep! He doesn't need to!
Okay, this is where your G-Spot REALLY IS. Your G-Spot can be found roughly 2 to 3 inches into your vagina, on the top-most wall (looking form your boyfriends perspective, it would be on the upper part of the vaginal "tunnel"). You can tell if it's your G-Spot, it should feel a bit different than the surrounding skin (G-Spot is circular in shape, about the size of a quarter). Try to find it yourself next time you masturbate alone, and make sure your boyfriend STOPS what he is doing!
I hope this clears everything up. Let me know how things go after this