Is he cheating on me?

Ok, so earlier today my friend, he's a guy, texted me asking if i trusted my boyfriend, && i obviously said i did && demanded to know what was going on. He told me there was this girl in their P.E cl all over him && he wasn't doing anything to stop her. I know her, && ive never liked her, she is simply a skank with every single guy in school. My friend said the way she looked at him was just wrong, like she was gonna eat him. Several people have come up to me && told me the same thing, but i still haven't confronted my boyfriend about it. The confusing part it, that friend who told me about the girl && my boyfriend keeps sending me this weird little message telling me my boyfriend isn't enough man for me, && this whole bunch of stupidities. I was planning on talking to my boyfriend about this when i actually got proof of it. I know he wouldn't cheat on me, he isn't that kind of person, but even though i wanna trust him, there's a part of me that is still doubting. Should i wait for more evidence? confront her? Or him? Pleaseeee help me!