Pressure during sex?

Hey everyone,

I'm 19 and had my first time at 16 where i bottomed. Since then i only had sex 2 times because i wasn't really feeling like having sex. Me and my bf have been dating for 3 months now and i really wanna have sex but every time we tried it, it hurt like hell because he's on the bigger side of things. No matter how much prep we did and if he gets it in it still hurts and it feels super weird like theres so much pressure inside. I can't remember feeling like that at any point before when having sex. So does anyone have 1. prep tips and 2. tips for maybe getting rid of that weird ass feeling?