what should i do?

i have know one guy on facebook. i don't usually chat with any stranger but he looks like he know me so i reply his chat.. then,we started to chat until he ask for my phone num. i start to like be friends with him so i gave my num contact and finally i fall into him. i think he like me too. i'm sure but one day i find out that before this he already love someone. i add that girl too so i can find out more about them. that really hurt. i try to leave and ignore him but he will call call and call me until i answer the phone. i lost confident. i don't know where he really like me or just play with me. i try to deny that i like him. i treat him less. but my love feeling towards him more big although i never meet him in real life. we only chat,message,call and whatapps.. what should i do? i hate this feeling. i want to become him. n i have imaginary to marry with him too.. but that girl? what is he actually feeling towards me? i want to finish and out of this feel.. it give me stress n feel sad.