ok, first of all u need to stop, just stop thinking about her. i know that is hard. i have been there. she is gone, history, she wasn't good for u and ur self esteem anyway. stop pineng over her cuz that is not gonna help u. u need time to heal. u don't need another relationship too soon cuz that's only gonna be on the rebound.
what u need to do is take care of u, spend time with u, work on ur self esteem and bring it up to its highest. examine some of ur own flaws, see where u may have gone wrong. fix u. make urself a better person. get spiritual, get off this lonely kick and get out there and find interesting things to do. make urself busy. stop being negative and practice positive thinking. empower urself, make urself more attractive so that someone will want u and keep u. i don't mean beauty, u need to be attractive on the inside too. let people fall in love with ur brain. it takes a whole lot to make a relationship work. people want to see and be with a positive, confident u.
find ur joy, inner joy and happiness and let that radiate out so others will see and find u interesting to want to b with u. stop, look and listen to what is going on around u. practice cognitive self discipline. sometimes we can't always follow our heart and have to follow our brains. thiink about u and how u can make someone else treat u special. think about what makes u tick. the next person is gonna want to know.
if u don't know where to begin, or don't understand what i am saying, those times when u feel lonely and u r home, go online or go to the book store and find material on self development, relationships etc. there r tons of materials out there to help people discover themselves and make u a better u. seek and ye shall find. also, reach out to God and pray and believe and he will guide u.
u have to understand urself first b 4 u can get into a relationship. the qualities u look 4 in someone, make sure u have them all or close. u have to find someone who is compatible with u and if u don't have things in common, the relationship won't work. for the relationship to work, u have to focus on what u appreciate about the other person and not their flaws.
i hope all this was helpful. good luck in the future and remember, do onto others what u want them to do unto u.
the success of all relationships depends on compatibility, shared interest, friendship and trust.