For Men
1) Listen. The situation involves more than just you. There are now three lives to think about.
2) Stay Calm. She needs your support now more than ever. She may be carrying the baby, but you are BOTH parents, and regardless of your relationship in the future, that baby needs you too.
3) Talk about it - not only with each other, but prepare to talk with parents and others close to the situation. Hiding the news from people who can genuinely help you only increases the stress.
So you think she might be pregnant.
Here's some quick advice that may be of benefit to you right now: