reocurrent bad dreams..help

so maybe i should just say 'nightmares'?
altho i assosicate nightmares with scary feelings, the feelings in these dreams are not scary, but painful always the same:

anxiety, trapped, belittled, frustrated, my heart in pain...

my ex who abruptly broke up our relationship (long distance relationship which was very strong and more meaningful that anything i've had in yrs)and left me in shock...keeps appearing in my dreams. sometimes as my friend (which confuses me) sometimes as totally evil,manipulative and twisted and out to hurt me..i try to wake mylsef up from these dreams some nights. i want him gone. i want to forget. i wrote him out of my life almost completely now, i know it sounds cruel but this is the only way i could deal with the pain, yet he keeps coming back in my dreams. after breaking it off abrubtly, he wanted to remain friends, i felt like my heart was ripped out yet he wanted to be friends? so now i feel like i'm haunted. im told it's my subconscious trying to deal with it, but i don't understand the dreams. i've moved on, so has he and yet, these ghost images - my dreams...out of no where, especially when i've gone weeks not thinking about it and feel great. then boom. i wake up feeling horrible, in emotional pain and it stays with me all day. i want my life back! when i get a grip on it in reality he takes it away in dream!

why is this happening?