what should i do me and my best friend thats an opposite sex like each other!!!!!!?

[Lydia]

im 13 and i have a best friend whos a boy and im a girl and hes 12. hes a 6th grader and im a 8th grader. we text each other every day and we are also neighbors. we usually see each other everyday but lately he has been really busy. anyways when we text we play a truth game where we ask each other questions and when we answer we have to tell the truth oneday he asked me if i like him and i said nahhh i like you as a bestfriend i wouldnt want to ruin our friendship and i asked him if he likes me and he said sorta but ive always realllllyyyy liked him and i need advice on how to tell him that i really do like him