I have been through this with someone before. Have you thought about seeing a healthcare provider about it? Are you on an SSRI? They can def lower drive. As can other meds. As can other endocrine problems and physical health issues. As can a history of abuse or current relationship issues. There's a bunch of potential causes.

In my experience, sexual problems in the relationship often lead to bigger problems. So, if the relationship is important to you, you might want to look into this a bit more proactively. It is not unheard of for partners (of either sex) to become impatient after awhile and they may seek to meet their needs in ways that are not helpful to the relationship. Best of luck to you!!