Strange guy

Hi guys, I am going to share with you my actual situation with you cause I really don't know what to do, and your advice will be really helpful for me. I am a student and I had some lectures with another class program for one semester. There was a very handsome guy, I liked him since the moment I saw for the first time, but sure I didn't let him know that. After sometime he sent a friend request on facebook and we talked for about 2 weeks or so. But actually were just general conversation but sometimes it seems like he was hitting on me. Sure I was happy but nothing was concrete yet. One day he disappered, he never wrote me again and on the classroom he stayed only with his friends. I was surprised why this reaction from nothing, but anyway I didn't write him. After around 2 months without hearing from each other we met at a party. There he tried to talk to me and to dance close to me.I have to emphasize that he was drunk. At a moment he invited me to go outside and he told me that he liked me but he could't do anything cause he was already in a relationship. Then he told me about the problems he had with his girl cause she was living far away and he was quite fed up with this. Again after the party, not writing anything for over 2 months. Then, one day from nothing he sent me a message if I would like to go with him and his friends on the beach. I was busy and I couldn't. After some days we talked a little and again he disappeared for 3 weeks, then again he wrote if i want to go for a barbecue. What really surprised me was that he was going with his best friends, who I didnt know, and he invited me. I have to say that I really like him, but I am afraid maybe he wants just to use me and that's all/ Please give me your advice, I am grateful if you would suggest me what to do

@SUSSIEDQQ I don't want to text him and ask why he dissappears and then show himself from nothing. I wanna know why, but on the same time I don't wanna let him know that I was thinking about him and so... Do you thnk is better to ask him directly about that?