In relationships we are constantly evolving and changing (thank God). I think the time limit you gave her is more than fair. You did say one thing that stuck with me;

"This whole issue now makes me feel like I just can't do enough. I just can't offer enough, I just can't do anything right"

Have you felt this way about yourself your whole life or in other relationships? maybe an old partner or one of your parents? Your partner wanting kids has nothing to do with what you have to offer him/her.

Is there a chance you could reconsider your position on this? Keep posting.