help!

ok. im having boy trouble. theres this cute boy at school, longish blonde hair and dreamy brown eyes. he keeps flirting with me and i flirt back. we keep looking at each otherand hes just so addictive. i keep catching him look at me when i look at him, then he instantly looks somewhere else, occasionally smiling at me. this has been going on for nearly two years. ok. now theres a catch. hes got a girlfriend, but not the best, they hardly ever talk to each other and she is always moaning, theyre hardly with eachother, so i get away with flirting with him, but its kinda hard at the mo coz im on crutches.. but he holds the door open for me and helps me out and stuff.. cute! so i dont kow what to do. theyve nearly been goin out a year but ive always loved him longer than that. lol avrils new song 'girlfriend' fits perfectly. please help me, i dont know what to do now. if i reli get it going on him, ill feel reli guilty for his girlfriend but if i dont, im gonna be reli unhappy for most of my life, and i think he reli is my true love. i know we both feel reli passionate about each other, but i just dont know what to do... please help! give any advice possible, im reli stuck here.