Choices and conflicted feelings

SO things have been chugging along beautifully with Eli. He is robust and big and healthy and BOY through and through. There is nothing soft and frilly about him. No, he is loud, brash, tough, and just as flirty as can be. Total opposite of girl....that's for sure. And time is flying by. He is 6 months old already and I can't believe it has gone by so fast. He is no longer the little infant but a scooting, eating, yapping, bouncing baby. It's amazing!!! So on one hand I should be grateful for the miracle that he is and call it a day, right? I am, after all now considered "advanced maternal age"......ugh. I can't even type that without sneering. But when we look at him and hold him my hub and I can't stop thinking about maybe another. Maybe one more so he can grow up with a sibling more his age. Iris is great and loves him but she is 10 years older. Before we know it she will be out of the house and Eli will be by himself. That happened with my younger brother and we are only 6 years apart. He says he always felt so disconnected from my older brother and I and kind of lonely. I don't want that for him. On the other hand, I want to finish my doctoral studies, get more on our financial feet, have Iris more stable emotionally, and I have to admit, I am liking being more in shape again (but I looove my body pregnant just not the after part so much). We are torn. We don't want o wait too long as we want to be young enough to enjoy our kids but not sure the timing is right......ugh what to do what to do. The fact that I haven't gotten my monthly cycle back yet kind of is deciding it for the immediate future. Maybe I should just let it go.....cause I do that SO well....;)