Pregnancy worry/excitement

So I just told everyone we're expecting. I am a very cautious person and very private person. This is my first baby and I am always scared that something may go wrong. Well, one of my friends overheard me talking about my pregnancy with another friend and she mentioned that I didn't sound very excited. Wow! This totally crushed me. I am SO very excited, but I am also so very scared that at any moment something could go wrong and I could be without this little baby inside me. Therefore, I am very reserved about my feelings because I feel like my heart would be so broken if anything were to happen. How should I feel about this? I don't want people to think that I am not excited and I also don't want to explain to everyone why I am reserved about my excitement. Please advise. Should I go back to that person I was talking to and mention that someone else noticed that I didn't seem excited and make sure that person knows that I am in fact overjoyed?