If someone has wronged me by emotionally putting me down over years, and I'm unable to overcome what they have done or said to me, I can't forget it, unable to forgive that person what can I do, that oppression those thoughts come over and over again in my mind

Remind yourself that you have Allah with you and He will compensate you. Allah knows of your emotional suffering and so ask Him to compensate you. Maybe this bitter experience you went through and will prepare you to pass the trials of life in the future. Didn’t the brothers of Prophet Yusuf (a) gang up on him and hurt him and made him miserable for many years? But in the end Allah compensated him. Just remember that.