Boyfriend pressuring me to have sex

So I have had a boyfriend for about 1 month now. He asked me to have sex with him starting from week 2 but I said I wasn't ready which he unhappily accepted. Recently he keeps asking me every time we make out if we can have sex. He claims he only wants to do it one time just to prove to him that I can do something just for him. And that I don't have to do it on a "regular basis". He says that he has done things for me that make him uncomfortable (however none of those were sexual). He says because I have done it with my ex there is no reason I shouldn't be ready but to be honest I have only had sex 3 times (all with my ex) and I didn't enjoy it so I don't want to have sex for a while. I really don't feel ready to have sex with him yet. However he keeps getting upset about it and asking me why I can't do it with him but I can do it with my ex. What do you guys think? Because I think it's not okay and that he's trying to guilt me.