Okay so basically it wouldn't fit

So....I recently had sex with my boyfriend for the first time...I was his first, and it was our first time being together, I mean. Anyway, I'm small and he's like, twice my size, and maybe it was because I was standing up, but it actually WOULD NOT fit. Even when I was straddling him, it wouldn't o all the way in! 😣😣😣😣He has like, an 8.5 inch....how can I make it fit next time?