Funny, I was never interested in having kids & maybe even didn't like children very much .... but then I had my son, and WOW, this is the best thing that's ever happened to my husband and I. We love that little boy so much, it's just overwhelming sometimes. Every day is fascinating b/c he changes so quickly. Honestly, where once I often declared that I would NEVER have children, now I wish that I had him earlier (pregnant at 34, now 35). I used to scan the internet for info about whether people with children are "really" happy, and wondered if anyone regretted their decision to have kids. Looking at other people's children, they never seemed cute to me or stirred any maternal feelings. I even thought that people who had kids were settling for less & would lose all their freedom & would become boring and one-dimensional as individuals -- how wrong I was! I was so naive and judgemental of people who chose kids, and just plain wrong. Thank God I was lucky enough to accidentally get pregnant!
I look back on my life before this child, & my previous life now seems so meaningless -- though I would have not understood this before having a child. In other words, it's really something you've just got to experience in order to understand -- and I doubt having a 9 yr old stepson can compare, b/c he doesn't feel like your child to you (ie. you haven't raised him since birth & experienced all that reciprocal love from your own baby). You can have a wonderful life childless, but it won't reach the depths of emotion & breadth of personal growth that comes from having a child -- it broadens your world in such an incredible way. I say go for it, you won't regret it (after the first 3 months, that is *LOL*)!
All that said, having a child is THE HARDEST thing I've ever done. It's exhausting a lot of the time, and I'm constantly sleep deprived. It's harder than nursing, for sure. Regardless, it's worth it. It stretches you as a human being, it completely opens up a new world, it's fasinating, and it's fun!