Of course it's normal to feel the way you do, having a baby is a massive life change. If you weren't worried at all, that would be concerning.
My DH and I are trying to conceive. I have 4 of my own already, he doesn't have any of his own. I know I will worry when I do fall pregnant, was it the right choice, can we really manage, what if we can't cope and end up splitting etc etc. All natural and normal when faced with a huge hypothetical thing becoming a reality!
I also know, however, from having four already, how amazing and special it is, having children in your lives. Watching and helping them achieve, seeing them go from babyhood, to toddler, to child and in my case, my eldest is about to be a teen. They have brought much more depth to my life than there ever was before them. A meaning as such. For example, all the mistakes and unpleasant stuff that's happened in my life, now has a reason and meaning: so I can help guide my children.
Honestly, hang on in there and try to avoid reading the bad stuff. The internet always gives a very one sided view.