Penetration hurts????

I’m 18 and my boyfriend is 20. We struggle to have sex since I’m so tight and to me he’s so big. So I got a dildo to practice. Missionary position works very well but and other position hurts like hell. I started crying and thinking that I’m useless and I won’t ever get to have sex the right way. Someone please give me some advise? 😭😭😭