How to forget your love whereas it is impossible to do ?

his ex had been to U.K. 4 a new living n by den talking to him was wat i was glued to........suddenly our friendship changed into a relationship. I started loving him very badly........he was also pretending dat he loved me alot. but after 7 months his gf had returned to his place again and nw hez expecting me to be his best friend n make his ex.....his girlfren.......!!!!!! i hav never seen datperson in reality i felt in love wid him by talking on the phn.......hw stupid of me but cant help it as i hav already done dat fault !!!!!!