is there such a thing as too small?

okay so my boyfriend and i have been trying to have sex, he’s a virgin and i’m not. the other thing is we’re 14, ive had a lot of sex before which probably sounds like nothing given my age but anyways, we can only seem to get the tip in but nothing more. i have never had this happen to me or even heard of this and i was just wondering if it’s like normal and if there is such a thing as too small to like fully get in.