:( My new guy best friend is so nice with me but I didn't know he likes me until last week but I don't know what to do!!
I think I like him but he doesn't show that he likes me when I'm around him!!
So I don't know if it's true or not!!
What can I do to proof that he does like me?
Should I go out with him or should we just be friends?

Once you go out with him, it will be fun for awhile, then eventually you two will stop dating. That IS what happens when people date. 95% of all dating couples stop dating, some date a short while, others date a LONG while, but in the end almost ALL of them stop dating.

When that happens, you'll no longer be dating AND you'll no longer be friends. You can try to turn this friend into a "date"... but remember, when the dating ends, you'll lose your friend, too. Make sure that's OK with you before you even start.

I think you should go out with him. Most likely he's too scared to act like he likes you because he might think you don't like him the same way back. But in the end he might be that type of guy who doesn't like being friends with his exs, or he might. So you do have a chance of looseing a good friend.