At the risk of being minimalistic here, having read your situation it seems to me, that you simply need to go to confession/reconciliation…receive absolution for your sins, (whether mortal or not…it’s kind of irrelevant if they are haunting you), and then, with a contrite heart, and invoking the intercession of Jesus and the blessed virgin, endeavor to not sin, and to avoid that which causes you to sin. It sounds like you know what sin IS. I wouldn’t spend too much time worrying about the level of it, whether mortal or venial. Just pray for virtue, attend mass, go to confession, be absolved, take communion, then go out and be a light to the world. This, frankly, is all ANY of us can do. It’s the system that was set up by Jesus Christ, the Lord. If you have a habitual or addictive sin, I can recommend from personal experience that you find an accountability group like (AA, NA, OA,SAA, Courage, etc.) whatever is appropriate, get a sponsor, work the steps, while going to mass regularly, (including receiving the sanctifying grace offered in the Holy Eucharist), and have regular confession and absolution by a priest. Repeat this cycle until the end.
This is intended in all charity.
The Lord be with you. I have just prayed for you. Please pray for me as well.