Why cant i find a guy?

I am a good looking female im not bragging or anything but I always get approached by guys or have them look my way. But, the sad reality is that I can't keep any guy for the life of me..and the one ex boyfriend I had didnt even care about me. He was a complete meat head and all into himself, yet he never cheated on me. I am starting to believe I am unlovable and unable to ever find someone. I believe it was my ex might have changed my personality a little bit into a very shy person since he was always very jelous and never showed much emotion at the same time (doesn't make much sense but its true). Its just depressing because I see many good looking girls get boyfriends so easy! I mean im slim 5'5 118 pounds and have black hair tan skin and blue green eyes. Please help…it would be greatly appreciated! Also, I'm 22 and very successful and motivated with a sweet loving personality :( .