Quiet betrayal is still betrayal
Microcheating is still cheating.
Stop trying to water it down just because there was no physical contact. Loyalty is not only about what you do in person. It is also about your respect, your honesty, and your intentions when your partner is not around.
Entertaining someone else, hiding conversations, flirting for validation, or acting single while you are in a relationship already crosses a line. You knew what you were doing, so do not hide behind excuses now.
If you have to delete messages, keep things secret, or make your partner question your loyalty, then deep down you already know it was wrong. Calling it harmless does not erase the damage it causes.
A real relationship should feel safe, not confusing. And betrayal does not become acceptable just because it happens in smaller pieces.