Three words, different stages
Perimenopause is the transition leading up to menopause. Natural menopause is usually identified after 12 months without a period, when there is no other cause. Postmenopause is the time afterwards. Hormonal contraception and some treatments can make the picture less straightforward. A clinician can help you understand your situation.
Your experience may be different
Menopause can happen earlier or follow medical treatment. This guide is a starting point, not a way to diagnose yourself or decide when to stop contraception.
One useful next step
Write down what has changed and when. If your periods change or stop before age 45, arrange a medical review. You do not need to wait until your periods stop to discuss troubling symptoms.