I'd also like to add that I think those who choose not to have are children brave. In no way does honesty constitute selfishness.

I was misdiagnosed with polycystic ovarian syndrome as an adolescent and told that getting pregnant would be difficult. When DH and I got married I missed my birth control pills for two days and boom I was pregnant.
We had been married less than 6 months and had dated for around 6 months prior to being married. We were in the middle of a job search driven by his research niche and within 14 months of being married: had a baby, our first house and two new jobs .Add to that I developed severe postpartum depression that I refused to acknowledge until my husband got scared out of his mind when I suggested he have a affair since I was incapable of being emotionally or physically intimate.
He found me the one woman whose entire clinical focus was on depression in women related to birth, menstruation, etc. She also did her counseling- something less than 5% of psychiatrists in the country do. She saved my life.
Like Una says being a mother has opened up my life in so many ways and I will say that unconditional love is perhaps the one thing that I would have never experienced without having a child. The reason I miss my Dad so fiercely is he loved me like that: unconditionally, in spite of, despite, because of.
For severe bleeding issues I had an endometrial ablation 2 years ago in order to survive adulthood without constant iron/blood transfusions.
The only way we could have another child is through surrogacy. We talk about this. Bebe wants a sibling. In our hearts both DH and I want a sibling for her and another child. But I know deep in my psyche that having another child even if I do not 'birth' the child myself will strip me of my emotional and physical strength because I am a tigress mother.
I feel selfish for other reasons: I want to have another baby, I want to give my daughter a sibling, I want her to have family after we are gone, I want her to celebrate holidays with loved ones. But I am not sure that I could survive raising another child because the constant anxiety and worry that I face with a baby while it may be better monitored and controlled will not give me the 'me time' that I have learned the hard, hard way that albeit I may seem selfish is what allows me to stay alive.
In the end having one happy child and one happy mom and a happy family will need to trump my desire to give my husband and daughter another sibling and child. And of course me too: I want another child but I am too fragile to be able to devote most of my time to looking after another infant even with help and adoption is out of the question for us for family reasons. I have to make peace with my own demons everyday. My baby sister is pregnant with baby #2. She needed a lot of infertility treatments to have baby #1 and her ob/gyn never expected her to ever be able to conceive again.
Am I jealous : Yes. Do I want to actually be a mom again: not so sure at all.
Peace for me is so fragile. I feel afraid to tilt the scales even a bit. I have never had a 12 month free period of a serious attempt at self harm in the 7.5 years since bebe was born. Self preservation or selfishness: maybe a bit of both but it seems like bebe will be an only child.

Sona;
As your daughter grows older and observes more families including adults, she will see that not all siblings get along and that some are estranged from one another even as adults. Sometimes they make one another very, very unhappy. Thankfully, my DD understood this early on and never asked me for a sibling which probably would have been impossible anyway since I had her when I was over the age of 40.