I need help with my guy friend....?

Ok, so I have this guy friend I have known for about a year and a half. He is the best friend I could ever have, almost like a brother to me. He even likes to call my mum, "Mum". He tells me everything, and I tell him everything....at least I used to. He is starting to look different to me, I don't know why BUT I don't like it. In the past my family used to make fun of us being "Love Birds", even after I clearly stated that we were nothing of the sort. Some small part of me wishes we were. However small it may be. I know his family as well as he knows mine and we get along super well. The other day we were on my roof eating pizza when he stated "This is romantic." I was confused, because I was pretty positive that I liked him 1/10 and he didn't like me. But I guessed it could have been him making fun of the situation, because he is always trying to be funny like that. He always says he loves me, but I'm pretty sure it is the friend way. We do literally EVERYTHING together that friends do and it is just painful to not want to hurt what we have but to sort of want what everybody THINKS we have. Lately, he has been talking about a girl he likes A LOT. This is normal for us, and I always help him with his girl problems, but this is the first one that has come up since I decided that I might maybe possibly like him. And it bothers me more than it should. Apparently he noticed because he said "Hannah, what's wrong? You get a weird face whenever I mention Brooke." I told him nothing was wrong but he said "Hun, I'm your best friend. I know you inside and out, I know something is wrong." I know he called me Hun as one of his jokes, but still...it gets to me. I told him I couldn't tell him and we now have an agreement. If he can book Ringo Starr for my 16th Birthday party, I have to tell him the first secret I've kept from him since we met. I know he will never do that, so it will be easy to keep the secret... But I don't know what to do. Please give me advice, because now every time he brings up a girl, I get slightly jealous, stressed, and want to tell him what I'm starting to feel which SHOULD not be there. I know this is long...but...help....please