Scared to let him go further

So me and this guy are getting pretty serious and we make out a lot in his dorm and I’ve given him a blowjob. I think it is worth mentioning that he is really respectful and asks what I am comfortable with. One time he asked to finger me and I said no, and he respected it. I do want him to be able to pleasure me but I have never had anything up my vagina before and it scares me. I’ve never even used a tampon (I’ve tried before and it just hurts) so I can’t imagine how a finger nonetheless and penis would feel. I really like this guy and want to have sex with him though. I am just terrified it will hurt too badly or it won’t go in. Or I will try it and hate it and never want to have sex again. He is also a virgin. I’ve talked to him about being nervous before and he says “you have nothing to be nervous about” and “you’re totally safe with me i promise” but i still feel scared :(. Has anyone ever dealt with this and how do I overcome it?? Any tips on how to just relax?