Question about postpartum depression

So... I obviously had a baby in March. I also had a baby November 2015. He’s three now. Apparently concern has been raised that I have postpartum depression. But my first baby was diagnosed with a terminal disease which I am a carrier for. So I can’t have babies unless I risk them having this disease. Thankfully my second doesn’t have it. I feel like I’ve been fine, I have been sad about my first child dying, and the fact that I can’t have all the kids I want, but I feel like that’s normal??? I don’t feel like I have postpartum depression. I don’t even know. When they told me that, I started questioning myself. I thought I was fine??? And going through the normal stages of anticipatory grief???