Should I still like him?

Theres a boy in my year in school who I really like and have done for about six months now. He's a bit of a ladies-man, he's been out with about five girls since year 6 (so ive been told) and he has a girlfriend now. Im not plotting anything that will make him like me and forget about her, i dont want to ruin their relationship but I just need some advice on him. Even if you have a girlfriend, at 14, you might have a slight crush on other girls. Idk if he likes me, heres some things he does: Most of the 'flirting' happened around christmas, when we had to stay after school to perform our school pantomime. During the week he..: -asked if I wanted to have lunch with him and his friends (without his girlfriend) -smiled at me a lot! -I was a childrens TV character so my outfit was weird and he constantly stole the hat to try and get me to chase him around the room. -Looked at me a lot when he had to stand on stage etc. -He talked to me quite a lot (we both share similar interests) -He ruffled my hair to mess it up then smiled at me for ages. -He interrupts my conversations and listens to them whenever im near him. They're more or less everything that happened but now, he's quite distant and rude to me. We barely speak but I tried to pull a tiny prank on him the other day and he didnt even look up from his phone, he just said "no i havent" really rudely and it kind of got on my nerves. He was sitting next to his girlfriend at the time so I sort of got the feeling he doesnt want to be nice to be infront of her, could that mean anything? Im just so confused right now, he doesnt follow me on any social network site or anything but then again, his girlfriend is on every site he's on. If he doesnt like me, can you please suggest any ways for me to get over him? I'm falling for him more every day! Thanks:)