Scared and not sure

A couple of weeks ago my partner and me decided to try to have a baby. We have been together for several years after both coming out of difficult marriages. This year is our 40th birthday, so we feel there is no time to loose. I am scared : what if this relationship breaks down, what if I am too old for this, what if I will not like having a baby, and many other questions.
Day in day out I question myself if this is the right thing to do - but how to find the answers ?
Would love to get your input of people who have been struggling with the same questions