D.W.
I have a different perspective because I was diagnosed with cancer after the birth of my second child (the day before my son's 2nd birthday, and 2 days before my 33rd birthday.
Instincts are a funny thing. I would have thought I'd melt into a puddle of emotions. Instead, I was very resolute and determined to do everything I could to beat cancer. And, so far, it's worked. Interestingly, though, I really wasn't as afraid of dying as I was of not being able to be my children's mother. I wanted to be a mother, and I don't want to leave this world before I'm finished teaching them what they need to be independent, individual members of society.
We can't control much in our lives. But, we can choose to be present in our lives and the lives of our families. Anything could happen any day to turn our worlds upside-down. Make the moments you do have count.
I can't tell you not to worry or to turn your anxieties into something more positive - we've all been there. If you have the love in your heart for another child, talk it through with your husband and make the decision that is best for your family.
Best wishes.