so bored, help

so me n my bf have been going out for 4 months now. we’ve never really sexted before because whenever he wanted nudes or something i always said no cause i’m not like that, he always respected that and doesn’t ask anymore. i know he’s not like me and he likes to be a little dirty and likes sexting n stuff but he just doesn’t think i’m capable of that and still thinks i don’t want to. WRONG!! i realllyy want to do it now hut anytime i start he just changes the subject or doesn’t go through with it n im too scared to just straight away send him a full nude... help!!