is premature menopause real

I'll be 37 next summer. No kids. And every month for the past about almost 2 years my period gets lighter and lighter each month. Or as the months pass. So it used to be 5-6 days straight. With the first 24 hours of cramping. And now I get 3 full days of heavy flow, with the first 24 hours of pain. I have noticed my period is shorter and shorter with time. Are these the signs of menapause? My mom would say that woman in her family suffer from premature menapause. But she's nut job. And I asked my doctor which is a man. ( I know that doesn't matter) and he said I'm clear till about 51. So at around 50 I'll be dry. But how late is too late?