why does this happen?? 😭

So I'm 16 and I have a boyfriend. It's the first time I've actually gotten sexual with someone. He fingered me a couple of times but every time he does it hurts. He's told me that he only puts one finger in and not even all the way, and i'm already stopping him because it hurts. It feels nice when he's rubbing it but once he goes in, it really hurts. He's also said that he feels it tighten when I tell him it hurts. I thought it was because I'm a virgin and never had anything down there...but it continues to hurt every time. Is there something wrong with me down there? or is it completely normal for it to hurt?