I understand your concern as I am an athlete as well. When I first found out that I was pregnant I weighted 111lbs (my height is 5ft. 2in.), by the end of my 1st tri I was roughly 86lbs, horrible horrible morning no all day sickness. But, once the docs gave me a pill to stop the sickness (Kaiser they waiting 4 1/2 mns before giving it to me!) I gained 10lbs in 1mn! By the time I delivered my son I weighted in at 165lbs.
I know the docs say they don't want us gaining over x amount of weight, well I did. It was healthy gain, I didn't eat everything and anything an use the excuse "I'm eatting for two and I am craving it," like alot of pregnant women do.
I feel as long as you eat healthy, with the occasional Reese's Peanut Butter cups like 20 in one day, you will be just fine. I did walk a lot during my pregnancy, we just got a 5mn Boxer 4 weeks before I found out I was pregnant so he helped me stay walking throughout the pregnancy and I believe that helped me lose all the weight.
My son was 9lbs 2oz and was 21 1/2 inches at birth. I lose my weight very quickly. I had my 10 high school reunion about 2 mns. after my son's birth and I was wearing I size 3 again by then. My son is 2 1/2 yrs old and I weight 113lbs.
My main advice to you would be just don't worry about it, walk everyday and eat health. Just be an athlete!
Hope this helps,
Mom of Dean