Congratulations! These are exciting times. I am a triathlete and a professional who cares for pregnant women, and a mom.
You are concerned that pregnancy will affect things. You are correct. But, it isn't forever and assuming no unexpected complications you can maintain a lot of your fitness. Women who exercise regularly have less risk of diabetes in pregnancy and a higher chance of normal birth.
Becoming a mother will affect you in many ways some of which you will anticipate, perhaps not all. Your priority while pregnant will be good health for you, and your child. Fitness can be a part of that with a few precautions. Here are some general guidelines from American College of OB/GYN on the topic. Good luck!
http://m.acog.org/...ncy?IsMobileSet=true