Why is it that a young man wanted so bad a child but now that he has it he feels sorry for his wife and all that he caused to her?
Presumably she was also happy to have a child; you didn't 'force' that on her.
Your feelings are actually quite normal. It's the reason why women, years ago, decided that a man did NOT belong in the birthing room. Now some men can handle this, but some, like you, can't. I would strongly advice you to see your doctor for a complete physical and possibly ask for a referral to see a counselor to help work out your thoughts. A baby is a HUGE responsibility - for both mom and dad.
Pregnancy and childbirth is natural and women generally feel pain when they go through it. It's been that way since the beginning of the human race and it's nothing to feel guilt over. At 23, she's a grown woman who made her own choices to have a baby. You said yourself, she was just as eager to have a child as you were. Yeah, she went through the pain of labor but it's over now and it's irrational to feel the way you're feeling because of it. You can't protect someone from everything.
You have the kind of hangups that are usually only conquered with counseling. Get a good therapist to work through them.
It's called empathy, and it's a good thing to have.
Take a deep breath, and as you exhale, say the healing words "it's not all about me". Repeat as often as necessary.
Stop feeling guilty and TALK TO YOUR WIFE about this.