A dip in libido in your thirties or forties gets misread more often than almost any other physical change, usually as a verdict on the relationship rather than what it typically is: a hormonal, physiological, or stress-related shift.
Perimenopause can begin years before periods actually stop, and declining estrogen during this window reduces natural lubrication and sensitivity well before most women expect it. This is physiological, not emotional, and lubricant and open conversation both help.
Sleep deprivation, chronic stress, and certain medications — particularly some antidepressants and hormonal birth control — are common, underdiscussed contributors to reduced desire that have nothing to do with attraction.
The most useful reframe: treat a libido change as information about your current state, worth investigating, rather than a fact about your relationship that needs no further thought.