Ok. To tackle your worries one by one (leaving aside the fact it's perfectly fine to not have kiddos - I am assuming since you've gone to the trouble of posting that you aren't 100% sure that you don't):
Pregnancy. Not particularly restricting - the food, alcohol, etc stuff you can use your common sense and go with what feels right. The first trimester is pretty crap physically - spots, daily vomiting and lots of migraines for me. BUT the second and most of the third can be lovely - you look and feel glowing and sexy, loads of energy (physically and emotionally) and people are incredibly kind to you.
Birth - I don't think this should be a reason not to have em, not on its own. It can be amazing or it can be horrendous, but afterwards it's over and you knit back together and actually, I've found it's made me feel incredibly fearless and strong. Plus it's an endless source of conversation with other mothers - I never get tired of talking about it :-)
Nappies. Hmmm. I'm quite a pernickety type, but it's just not as bad as you think. For one thing, when they are just drinking milk the poos are liquid and sweet smelling so although they get through lots of nappies changing them isn't really yucky in the way you think. Once they eat real food and do actual, proper poos they only do one or two a day and you can lob them straight down the loo in general (the poo not the nappy).
And the other thing that I think is impossible to appreciate before you have DC is just how bloody quickly it all goes by. When ds was a newborn the sleepless nights were tough. But they were over in the blink of an eye. So if there are stages you find hard then generally they pass quickly.
I'm not really 'good with kids' in that sense of finding it really awkward when eg a colleague or friend hands you theirs and you're not sure how to talk to or what to do with them. But I adore my own beyond all reason and its an emotion I really can't liken to anything I'd ever felt pre-DC. Life is bigger, better, brighter, has more meaning, now DS is in it. The contrast of my life before and after DC is as different as black and white telly and full colour.
But yes, it is the biggest undertaking of my life so far and changes you, your life and your relationship with DH completely - so nothing wrong with you thinking very carefully before you decide.