what has happened doesn't make sense

im 18 and recently my girlfriend broke up with me after two years of dating about a month ago, i can easily say they were the best two years of my life. we were both very in love with each other, but obviously she fell out of love with me pretty quickly as another guy came along who i suppose is a better person than i am. i dont understand how she can go from being so into me and then suddenly just decide to end our relationship and get on with another guy, i understand peoples feelings change but they dont change as drastically as this especially considering i didnt do anything wrong as she said "its me not you" im lost and confused. what do i do? should i try and get her back? or should i just completely block her out of my life to get over her? or should i try doing what she is doing and date someone else? i just want someone to connect with and dedicate myself to, i dont want it for the sex or anythin i just want a relationship, someone to care for and be with, iv made it clear to her that i want her back, i need some advice on what to do, im crazy about her