Hi Hannah! Congrats on your little one on the way!!
I'll preface this whole post by advising you not to panic! There's no reason to constantly worry about CMV (or anything else really!)...it's not going to be good for your baby or for you.
If you have never had the virus you should simply be more aware. The virus is transmitted through bodily fluids. So, if you still don't have the antibodies, washing your hands with soap often is key. Wash your hands after you've changed a diaper, fed or bathed a baby. Don't share straws, cups, plates, etc. Don't kiss on or near the mouth (cheeks are great for kissing!). CMV and mono are in the same family, so you'd avoid them the same way.
If you have a fever or flu like symptoms, let your doctor know. That is the most common sign of a primary infection.
Again, don't panic. I know that this is going to sound horrible, but stick with me...there's nothing you can do to avoid a CMV infection. You could get a shopping cart that someones baby had drooled on and you could rub your nose and end up with an infection. You could also step off the curb and be hit by a bus. The best thing you can do for yourself is to look both ways before you cross the street. The same goes for a CMV infection. The best thing you can do is to wash your hands, carry antiviral wipes (if you can find them) and go about your business. Thousands and thousands of women who have never been exposed to the virus have healthy pregnancies and healthy babies living their lives without thinking about CMV.
Does that answer your questions? Let me know if you have others!