Esp during sex.
http://pregnancy.families.com/blog/exercise-and-trying-to-conceive

Have you always been doing this, you don't need to start new programs to over exert yourself.

http://www.ivillage.com/trying-conceive-aerobic-exercise-safe-while-trying-get-pregnant/6-n-145439

Regular exercise is fine, and even encouraged. Whether you are trying to conceive or not, keep to your fitness level and any changes in intensity should be gradual.