my best friend likes me. what do i do?

hey guys. so i'm fourteen years old and my best friend has liked me since we met in sixth grade. i brushed it off because he is a trans male and back then still identified as a female, and i was like bro i'm not gay! (even though i am bisexual, i was just in denial trust me).

Now we are both freshman in high school and i have been seriously considering asking him to be my boyfriend. I've had on and off again feelings for him for over a year now and i'm incredibly scared to tell him. Even though he's openly admitted to still currently liking me, he has a date in his instagram bio (like this: ❤️6/30/17❤️)

And i can't help but feel like he has a girlfriend now. We talk about EVERYTHING and i am so scared to ask him about the date. Why didn't he tell me if he got a S.O.? I feel like as a best friend i should at least know before instagram does. I wish i had told him sooner before he gave up on me and went to someone else.

What do i do? Do i ask about the date in his bio? Do i ask if he's single? Or should i let it go and move on?