For a bit of balance...I was OK when I unexpectedly found my first was on the way when I was 29 and a week away from getting married.
I DID worry when Jr arrived and I didn't receive the "lightning bolt, instant, life-changing love" thing. I just felt pleased and overwhelmingly responsible for the little guy, but I didn't become a different person.
For me, it actually took weeks / months to properly bond with the little guy and then it was best described as that scarily vulnerable, falling in love feeling that you get at the start of a new relationship.
5 years, one more son and no. 3 on the way, I've never been fitter, am covering more bike miles and have been abroad every year. Its hard work. There are compromises, but life is good!