Short answer
Intimacy can decrease after marriage for many reasons, including stress, tiredness, unresolved disagreements, financial pressure, health concerns, changes in routine, or reduced emotional connection. A temporary change does not necessarily mean that love or commitment has disappeared.
Islamic Guidance
What Islam teaches
Islam encourages spouses to live together with kindness, affection and mercy. Marriage is described as a relationship in which spouses find tranquility and Allah places affection and mercy between them.
Practical Guidance
What you can consider
Discuss the issue calmly without blame. Make time for conversation and affection, address practical sources of stress, and seek qualified marital or professional counselling if the problem continues.
Sources
Qur'an 30:21; Qur'an 4:19.