How to tell my brother that I have sex?

my brother means a lot to me, he recently found out about my boyfriend. and he wants to meet him, I'm not scared of that I'm happy that he found out. BUT I want to be able to tell him that I'm sexually active. I know some of you guys are like what the f*ck? why would you want to tell him. my brother has been there for me forever, we promised eachother NO lying, and NO secrets. our promises mean a lot. I feel like he should know, I have a feeling that he sensing somethings up cause he's been different with me lately, that he always gives me this look.
I'm scared to tell him, but I want to.
help?

u should tell him if you really want to dont be scared your going to end up tellin him at some point rite? and if you can trust him enough y would you be scared?

cause as much as I care about him, I'm scared that he's going to hate me for it

 
How old is your brother?
 

mmm 21.
I talked to him last night. we had a really good talk.