kish....U don't divulge which one of U initiated the break-up nor a reason "why." Was it U, him or a mutual decision? In terms of responding 2 UR question, all of this information would yield U much more helpful advice from others.
I will however, make an attempt 2 give U some "experienced" tips 2 possibly helping U w/ UR concerns at the moment.
"I want to forget him," U say? Realistically, not 2B smug, but U need 2 forget about "forgetting" him. You've started out asking the impossible of URself. He was a part of UR life 4 a period of time.The emotions & memories U shared R w/ U & short of a lobotomy, traces of UR time w/ him will always remain in UR mind & heart (whether pleasant or painful)
If U haven't tried a sit-down, rational step by step process w/ URself, it's wise 2 do this. The tried & true, point blank list of the facts, as U C them, will cause U 2 put more serious thought into the situation & perhaps, less emotion.
It appears UR main focus is 2 heal from the pain, emptiness & regret U experience as a result of this break-up.For every fond memory, remind URself of the moments that caused U sadness & doubt. For every wonderful aspect of this person that obviously led 2 loving him, B honest & acknowledge his faults & those times U felt unloved by him. Keep that list close by 2 remind URself 2 deal w/ truths rather than fantasy. & then go forward to improving URself....mentally, emotionally & physically.
Give URself some "time." If this is recent, know that each day that passes, (believe it or not) will B better & brighter. If it helps 2 talk about him, then do it, whether U confide in someone or write URself a letter, purge all UR current thoughts of him. If just the sound of his name feels like a knife through your heart, the instant he enters UR mind, distract URself w/ sights, sounds, activities or people 2 block him from UR thoughts. It DOES work w/ a little practice.
Do nice things 4 URself. Enjoy everyday life & indulge in pampering YOU. Try 2 keep activities & conversations light & happy & don't further burden URself w/ other issues that cause stress. In other words, take care of UR body, mind & heart especially well right now while U R feeling "weakened."
Keep busy w/o tiring URself out, eat well & definitely exercise,( walk in the fresh air) .Being tired, hungry or immobile always magnifies any negative frame of mind. Do all of this w/ intention each day until U can literally "feel" better & happier. U'll be FINE.