Based on the context, by “sex” I assume you mean heterosexual intercourse, and you need to know, unequivocally, that it is not suppose to hurt, it is not supposed to be uncomfortable or painful, it’s not natural for you to not enjoy it, it’s not expected for you to bleed or cry or anything like that. Though it’s very rare for a woman to be able to orgasm from it alone, PIV can be quite pleasurable if you are receptive to it, meaning if your partner takes the time to engage in enough foreplay that you are relaxed and excited. Barring physiological conditions that do, for some women, make PIV painful, if your partner is willing to take the time to make you feel good and be ready for intercourse (which he should be, otherwise he doesn’t deserve to be your partner) then your “first time” can and should be absolutely painless.
That said, the only reason PIV is often considered a “chore” or a “pain” for women is because society expects women to tolerate engaging in it even when they are not receptive to it, which means it is often painful and uncomfortable, which makes women think it’s always painful and uncomfortable, which reinforces the idea that pain and discomfort are natural, etc. etc. Sex is not doing your laundry or going to the bank. You are not required to engage in it for any reason, especially not simply because your partner wants you to, and especially not if he is not willing to take the time to make sure the experience is equally enjoyable for both of you. Sex, even casual sex, is supposed to, on some level, be about intimacy and pleasure for both partners, not just the man getting off. If he is only interested in pounding away at something until he comes, the internet sells plenty of disgusting replica vulvae he can check out; you are not a masturbatory aid, you are a person who deserves equal pleasure if and when you choose to engage in intercourse. And remember, PIV is not the end-all, be-all of sex either. Penetration is one sex act in an entire world of ways to feel good, enjoy yourself, and get off. Chances are it’s also the one thing that won’t get you off, especially if it’s treated as the main event and not just one small part of the experience. Be patient, tell yourself early and often that you are not obligated to make sure the evening ends in PIV, and resolve to say no when you don’t want to do something and to tell your partner what you do want. Chances are at that age he doesn’t have a lot of experience either (and unfortunately has probably been groomed on porn), and a little guidance wouldn’t go amiss if he is eager but not skilled.
But seriously, kick his ass to the curb if he doesn’t respect your no, respect your wait, makes you feel uncomfortable, or only thinks about himself. Dick is abundant and low value.
I miss my bird so much someone pls send me a bird immediately