I cheated on my spouse and I am drowning in guilt
What you did caused real damage, and the weight you feel is your conscience working as God designed - but guilt is meant to lead you somewhere, not to bury you. David committed adultery and worse, and his prayer afterward is in the Bible for people in exactly your position: 'Have mercy upon me, O God... wash me throughly from mine iniquity' (Psalm 51:1-2).
God's forgiveness is complete for those who genuinely repent: 'If we confess our sins, he is faithful and just to forgive us' (1 John 1:9). Forgiveness from God, though, does not erase the work in front of you: full honesty rather than continued deception, ending the affair completely, and accepting that rebuilding trust takes years, not words (Proverbs 28:13 - 'whoso confesseth and forsaketh them shall have mercy'). A pastor or marriage counselor can help you walk that road.
Your marriage may survive this; many have. Either way, do not let shame convince you God is finished with you - he is not (Romans 8:1).
From Bible Navigator's study library. Scripture quotations are from the King James Version (public domain). This is encouragement for study and reflection, not professional counseling - if you are in crisis, call or text 988.