Why do I feel too ashamed to confess after falling into sexual sin?

The holy fathers tell us that with sexual sins in particular, the devil tells people before the sin: God is so merciful, he'll forgive you, God will have mercy on you. Then as soon as they commit the sin, the thoughts start: aren't you ashamed of yourself? This is so disgusting. How can you go and tell God this? How could God even stand you? The holy fathers describe this, which means either they fell into it or people they knew fell into it, and it's the same stuff people talk about now.

The devil is not doing anything new. He's playing the same old game, and it still works on people today. He's always over promising and under delivering, and people are constantly not getting what they think they're going to get.