I've been lying to my boyfriend about my age for months. how do i fix this

i need advice. i've been with my boyfriend for 7 months. im sixteen, he's seventeen. we've met in person a few times, we're extremely close, but i've been lying about being twenty the entire time we've known each other because we met online where we were both lying about our ages and it went too far and i've never come clean. i need to, but im so scared. my father said i was 16 to his mom like 2 months in to our relationship and i panicked and said it was a joke and we're about to meet up again for a few and i seriously need advice. what do i do, i love him so much, i can't believe i've gotten this far and i seriously don't know what to do with his mom, like. i need to come clean and that's gonna complicate things i need help asap