I want to be able to have sex

I posted Earlier so please don’t come at me but I just feel very discouraged. I can use tampons and I have had sex once but we couldn’t get it in. Other than going to my doctor to get a physical exam (I would Do that but he said I have to wait till I’m 21 to get the pelvic exam. Which I will do) what can I do try to get it in during sex or using a dildo. Would lots of lube help? What are some tips to relax. It’s literally the only thing in my mind rn 😞 I don’t want to dissappoint the guy