When cheating men get too close = broken heart?

hello all, I am struggling with some thoughts, and I want to know if anyone can identify with what im going through...I have been "just that woman on the side" for too long, at first everything was fine,I really didn't have time for a full time relationship and things worked out great but now my life has settled and i have strong feelings for someone who is committed to another, It hurts soo bad to see them together : { that I moved to another state..I mean it's crazy because in the beginning I didn't even care that he was with her but now it's like im on the brink of depression because im alone...Im not ugly or anything of the sort but my confidence is suffering because I honestly feel like im not good enough to be with ......Im soo mixed up with emotion, I feel used, deserted, angry as he//, jealous, and most of all heartbroken...dose anybody have glue??