Why do girls keep turning me down?

ive had at least 21 girls in a row turn me down. i dont get why im a very nice guy and definitly not like most others. i just got out of a 1 year relationship where i stayed with the girl even though she was 4 hours away which means i got hardly nothing physical out of it. She's the one who broke up with me but anyways even though im that nice of a guy theese girls still dont want anything to do with me. i was thinkin maybe its my approach but really all i do is try to talk to em. The most i might do is say your pretty. I dont use any stupid pick up lines or say anything disrespectful i usually just try to make conversation but most of the time they wont even reply or they'll reply and have me thinkin yes maybe i actually have a chance and then the next time i try to talk to em they dont reply lol i have NO girls that are friends that im close with or anything to try anything with i dont even go to school so i dont meet any the most i can do is try to talk to the girls at my old school on facebook but like i said none of them want anything to do with me. does anybody know why? maybe im just REALLY ugly and dont realize it? haha i mean ive always realized that i was ugly but now im startin to think im like repulsive or something but maybe i dont see it cuz im myself you know what i mean? but anyways i need help on understanding this