What Causes Late And Scanty Menstrual Bleeding When Suffering From PCOS?

Hi, I'm 31 with 1 child aged 3. I have always had extremely heavy periods to the point that I can't leave the house for 3 of my 6 days. I haven't had sex in 2 years except once on New Years Eve & my period started just hours later normally. My Feb period was also heavy as usual but late. This month I was late & my flow is incredibly light for me, like the last day of my usual flow. Could I be pregnant or are there other possibilities? I have always suspected I have PCOS but would that explain the sudden drastic flow change?