If I had a baby already before being diagnosed does that mean #2 is possible?

So I had my son unplanned 2 years ago and we just recently started trying again in January. I was diagnosed with PCOS last week and now of course I’m worried about our chances to conceive #2. I’m still learning everything. Does this mean I had PCOS when I conceived my son and I just didn’t have noticeable symptoms? Or did I just recently develop PCOS and didn’t have it when I conceived him? How likely am I to conceive again? My doctor didn’t seem concerned about our odds of conceiving, though she did prescribe me Letrozole for next month to help me ovulate.