He has a girlfriend?

theres this guy at school and ive only known him 2 weeks or so but we are really good friends and spend all our tim eotghter pretty much in hysterics. he was being really suggestive saying things like you should come hang out with me sometime and you have to invite me etc etc. and when we were in a lesosn he always asks me to go with him if he has to go to a different room. we had to go and get omsething out the cupboard the other day in the cl just us two and he was like nudging me and stuff. but then i saw him with his girlfrind and everytime hes with her and i see him he ignores me but any other time he smiles and waves and talks to me. i dont understand