😓I need help

So I’ve been trying to learn how to suck dick and it’s like my bf wont help like he wants me to figure it out myself so I watch porn and shit and it’s like I don’t wanna hurt hit but my teeth keep grazing him and idk how to fix it. And then he tells me to open me mouth wider like bruh my mouth is open about as wide as it can go I can’t help it my mouth ain’t big af. I just need some help on how to make it better so I won’t keep biting him and how to last longer cause my jaw get to hurting and my ass will stop 😭