Hey there.
You're 13 with raging hormones. Now with puberty kicking in and such. Thus questioning or being curious about the same gender is pretty much normal for teenagers, you'll be surprised how much teenagers around you and your age are going through the exact same thing.
It's good that you seem really attracted to a girl, and its perfectly fine to also be attracted to guy. I really suggest you just take the guy, slowly and don't rush. I mean talk a lot, hang out and such; do the normal guy things. Then maybe after a couple years see where things are going? "Do you still have a attraction to this guy" "could you picture starting a relationship with him?". If answered yes, it may be potential for being bi/bi curious. Just don't worry about it to much.
And yes, please try not to assume things. Just because he seems awkward around guys doesn't mean he' g@y or bi. He could just be on the shy type. Remember that just because a person posses
LGBT qualities in them does not mean they are. I mean I know people who possessed g@y qualities, but they were perfectly straight. The only way to confirm something is by that person. But at this early teenage age; I would not recommend asking him if he's bi/g@y. Like how I said, it just might be a phase for both of you, that could fade in the long run
But nevertheless, if in the future you should turn out to be bi. I really want to assure you that you aren't the only one. They're are Lott's of guys that are also
LGBT. Take for example me, I'm 17; and I have been curious around guys for a long time, and just recently I came out as bi.
Well hope I helped,
PM if anything