Do you think he likes me? I'm not sure...?

"I saw him in the hall flirting with some girls and he didn't say hi or anything." there is something kind of fishy about this. But then again he might not have noticed you. It really sounds like this guy is interested in you. See if he wants to hang out with you outside of school, guys like confidence so asking him will show that you are interested in him and may push him to ask you out. And then if he says no, dont take it hard on yourself. Just smile and say ok then carry on with your day like nothing ever happened. If it disappoints you that he says no dont let him see that it affects you. What grade are you in? That may help me give you a better answer.