Is he hitting my...guts?

So I’ve had this certain sexual partner for about 5-6 months now, andddd I’ll just add in that he’s probably the biggest I’ve ever had. And when we are into it and everything I get this feeling right above where the face of the vagina starts, but inside like he’s hitting something, and it doesn’t hurt, it’s just like a feeling that isn’t pleasant. Some positions I can do but when it hurts the most is in doggy, but with every position I still feel it whether it’s faint or not...I’m just curious to know what it is because it’s been like this the entire time we’ve been doing this and I just wanna know if there’s something wrong. And I’ll also add that he’s rough with it if that makes any difference.