Well... Love is pretty hard to read.
I'm currently in a relationship. And honestly, they didn't act any different from before... It might not be obvious. That's why you have to just come out and say: I like you.
There's six magic words to use if you do like someone:
"Will you go out with me?"
Just think to yourself. Six words. Six words. Six words. Nine if you include the "I like you".
Don't be afraid to be rejected. If they do like you... Well, you're lucky, aren't you?