I had precisely this dilemma until about six months ago. (Thank goodness for good spiritual directors!)
Part of the reason I so very much didn’t want children was that I viewed them as a burden, as one more “thing to do”, as a restriction on my being able to do what I wanted when I wanted, etc.
Another part was that I just am not that crazy about most kids. Don’t get me wrong: I’m 100% pro-life, and I hold firmly the Church’s stance on contraception in marriage. I don’t, however, see a kid and think “ooooh, I want one of those,” y’know what I mean? (Some girlfriends of mine are utterly baby- and kid-crazy, and that’s fine…I’ve just not felt that way.)
It took a bit of very solid spiritual direction for me to recognize that the first point was due in no small part to the fact that I grew up in a very abusive and neglectful household, and pretty much was a mother to my younger siblings. Sure, I cared about them as siblings, but I couldn’t love them as or be a mother for them, and I certainly resented the fact that I had to take care of them as much as I did.
As for the second point, I realized that while kids in general are not something I’m terribly thrilled over,
I am capable of love. I am still learning how to love, but I am learning. (Reading about the saints and good people and spending time in Adoration is helping me immensely on this front.) When my best friend had her first child a year ago, you’d have been hard-pressed to find someone as smitten with him as Auntie UbiCaritas, and when he crawled to me yesterday, grabbed my leg and GRINNED at me…well, let’s just say that this girl about melted right there.

I still don’t think I’m quite ready to have my own children, mind you, but I also know that if I’m supposed to have them God will teach me to love them as He loves me, if, of course, nowhere to the degree that He does! (Oh, and hormones help, too. For once, they’re on our side, lol!) ETA: He wouldn’t want any kids (yours or mine, they’re His more than ours) to have unloving parents, and if those parents ask for help, He’ll give it.