Answers
I cannot forgive myself for what I did.
Self-forgiveness is not actually a biblical category, and that is good news, because it means your peace does not depend on you being satisfied with yourself. What Scripture offers is better: a verdict from the only Judge whose opinion decides the case, already delivered. If He has removed it, holding on to it is not humility, it is arguing with the court. Confess it specifically, make restitution where you can, and then treat the matter as closed because He has closed it.
Go and see for yourself
If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
1 John 1:9
There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
Romans 8:1
As far as the east is from the west, so far hath he removed our transgressions from us.
Psalm 103:12