I think that my bf penis don't fit inside

Lube.

You mean you actually got out a ruler and measured the diameter of your boyfriend's penis to 1/10 of an inch?

That's a pretty unique kink... but then what would I know?

Spit on it!!!

Were you actually horny during the attempted sex? I have to ask this because there is people who fail at sex because they wernt horny enough.

Try using lube?

try ya asshole instead