I see many signs, but my spouse still refuses to admit being unfaithful. What do I do?

Without an admission or clear evidence, avoid making an accusation of zina (adultery), but you have the right to voice your concerns and state your needs. Islam tells us to investigate before believing a report: “then verify it” (Surah al-Hujurat 49:6), and this protects both sides from baseless accusations. Talk about the changes in behaviour you have noticed, rather than attaching labels, and watch how they respond. Ask for reasonable transparency as a way of restoring confidence. If trust keeps eroding and your spouse will not discuss it at all, a counsellor can help open the conversation. Protect your sanity and dignity throughout this uncertainty. See communication & emotions.