What Causes Stabbing Pain In Stomach And Lack Of Appetite?

Hello, sometimes I've been having this stabbing pain in my stomach area (left, my left). It comes and goes, I don't know what could be wrong? I've been always having trouble with appetite, I tend to eat irregularly, also have a mild valve regurgitation if that makes any difference. I've been diagnosed with PCOS and slight insulin resistance as well. I just turned twenty.