Trouble having sex for the first time

I'm 17 and I've been with my boyfriend for a year and a half. We've tried to have sex 3 times and it just isn't working and it's really frustrating!! When he tries to get in it's like he's hitting a wall after a few cm and it's painful for me. I know it's not my hymen because I use tampons and masturbate and neither have ever been a problem. My friends have suggested I'm too tense down there but i know I'm not, I love this guy and I'm 100% ready to lose my virginity to him. We've tried lube too and nothing helps. We have great oral sex but we're ready for the next step. Can anyone offer any help or tips??? They'd be greatly appreciated 💞