The whole thing about sex is that it is supposed to be fun. Its supposed to be a spontaneous enjoyment of each other's bodies. You can't help what you don't feel. You either feel the fun or you don't. If you have sex for any other reason, its the wrong reason. And, you end up feeling like a victim and bad about yourself.
Your friend sounds as insecure about his value as you, he just shows it in a different way. He thinks that he only has value as a man if he has sex, and you are the nearest possibility for him. He's not a bad guy, just a guy who is mixed up. He is feeling social pressure to have sex and it is clouding his judgment. His anxiety is making him say things that he will later feel badly about. If you cave in to his anxiety then you would both end up feeling badly about yourselves. His wanting to have sex with you is NOT about his wanting the spontaneous enjoyment. Its about his ego and about social pressure. Its for the wrong reasons.
If you care about yourself and if you care about him, you'll say "No" and deal with whatever reactivity he will have. If he can't continue to be your friend then he was never really your friend anyway.
Keep in mind, if you have sex with him when you don't really want to- you are doing something hurtful to both of you. You BOTH deserve better.:rolleyes: