Sex is something serious, but like you said, you can’t change the past and he can’t change the past. Now I’m not sure if he lied or something about having sex with another girl before because you seem upset about not being his first, but that doesn’t mean it’s not special. It was both your first times with each other, and doesn’t that make it special too? Either way if you really like him or even love him, you’d accept him for him, all of him