Whenever i am fingering my gf, I have noticed that there is some kind of big, round "ball" type thing inside the top wall of her vagina, about 3.5 inches inside. It feels like it's about half the size of a ping pong ball, and it is very hard, almost like a bone surrounded by a thin layer of flesh. At first I thought it was her g-spot, but i have never heard of a g-spot like this, however i am not very sexually experienced so i probably dont know what i'm talking about. I asked her about it and she said that she has no idea what it could be. I dont remember what she said when i asked her if it felt good when i touched it, but i think she said that it felt "kinda" good. she often complains about her stomach hurting a little while after i finger her and push up against the "ball" for a period of time. Does anyone have any idea what this could be?