Allow me to focus on two words in your post which I bolded.
We already know the morality involved with impurity, and the requirements of the Church, That leaves your feelings.
Feelings can be spiritually dangerous. And for certain feelings are not truth, right? Feelings are feelings, Truth is Truth. Feelings are subject to the ebb and flow of the human condition.
You feel ashamed and worthless, yet the truth is you are of inestimable worth in God’s eyes. So your feelings are taking hold of you and diverting your gaze from the Way the Truth, and the Life. God is telling you one thing, and you are putting your feelings ahead of God. The same strong feelings that lie to you to make you feel ashamed and worthless also drive you to satisfy feelings through impurity. It’s a vicious up and down cycle.
The key is to put your feelings and emotions in proper perspective -at all times-…when you are low, when you are high, your feelings need to be subordinate to the truth of who you are. Otherwise your feelings will have you on a rollercoaster of ups and downs. This is Satan’s plan, not God’s. The truth is that confession’s purpose is not primarily to make you feel better. The purpose of confession is the remission of sins. So you feel bad in the meantime. So? Feelings will pass. Use that time of torture to go to God and bask in his Truth.
When I get into a place where Satan is using my feelings and emotions to lie to me, I like to remind myself of a few things:
"my feelings are not god, you, oh Lord, are God. "
“That others might become holier and purer than I, as long as I become as holy and pure as you will, Lord grant me the grace to desire it”.
St. Thérèse of Liseux Prayer From “Story of A Soul”
“May today there be peace within.
May you trust God that you are exactly where you are meant to be.
May you not forget the infinite possibilities that are born of faith.
May you use those gifts that you have received,
and pass on the love that has been given to you.
May you be content knowing you are a child of God.
Let this presence settle into your bones,
and allow your soul the freedom to sing, dance, praise, and love.
It is there for each and every one of us.”