Being a father is difficult, especially during the pregnancy where men are supposed to turn into some kind of super human.
You will be asked to be a perfectly selfless, perfectly patient saint with endless energy and no emotional needs. In addition, any ability you have to read minds, or go long periods without sleep will be indispensable (and this is before your child is born). I understand women go through the physical challenges, but being the man in a pregnancy is much more difficult (with much less credit or understanding).
That being said, enjoy the time-- both the wonderful parts and the trying parts.
When you hold you child in your arms, it somehow makes it all worthwhile.