Hi I'm back!
So those changes that I mentioned get detailed in the With Pleasure article, but basically when someone with a vulva gets aroused, a lot of blood flow is directed towards the labia, clitoris, other parts of the vulva, which makes them swell up and become super sensitive, and, as you know, the inside of the vagina starts to secrete fluids that allow for easier penetration. Those physical things have to happen as well as
being in the right mental state - someone can be as physically primed as they can be, but if they're feeling uncomfortable, distracted, or just not into it, it can definitely interrupt those cycles of arousal and stimulation.
So you mentioned that you both felt nervous - have you talked with your boyfriend about the thoughts or worried you find yourself having?
You also said that you weren't expecting to get much physical pleasure out of intercourse beforehand - why do you think you feel that way?
What thewrit3r said was perfect, I couldn't have said it better. How we feel about sex, what kinds of sex we do/don't have, and everything else about our sexuality grows and shifts constantly throughout our lifetimes. If intercourse doesn't feel like your favorite cup of tea right now, that's okay! There's nothing wrong with sticking with things that you do like.