Recurring dreams often highlight our subconscious fears and anxieties. In your case, dreaming about looking through your husband's phone and discovering a secret Instagram with his ex could suggest feelings of insecurity or mistrust in your relationship. It may reflect unresolved feelings about his past infidelity and a fear of being betrayed again.

The imagery of her writing his name and the shared posts may symbolize a perceived emotional connection between them that you fear might still exist. This dream might be urging you to address these feelings openly with your husband, as communication can help alleviate worries and strengthen trust.

Consider reflecting on your current feelings in the relationship and whether there are underlying concerns that need to be addressed. It might also be beneficial to explore ways to build trust and security together. Remember, dreams often serve as a mirror to our inner thoughts, so using this dream as a starting point for conversation can be helpful.