T.,
Congratulations on your 'Babykins!' I think it's great you're walking a mile, but you don't say how often. I'd encourage you to do this at least 5 times a week. Exercise in pregnancy can equal fewer contractions and less pain in labor.
Now, nutrition. I would encourage you to not work to "manage" your weight, but to concentrate on nutrition and there's a huge difference. A really good website on nutrition in pregnancy is http://www.blueribbonbaby.org/. Dr. Brewer came up with a great nutritional plan. The thing to remember, not every woman needs the same amount of calories, so you have to adjust it to your life. But, it gives you a plan for eating well. When I was pregnant with my last daughter, I was also practicing as a homebirth midwife. I really liked the Brewer diet, but knew I didn't need all those calories. So.... I ate when I was hungry and stopped when I was full. But, I made my choices from the list. So, if I was light on vegetables, that was the first thing I ate next. I found 2 really good leafy green vegetables and made sure I had at least 2 servings each day.
Choose to eat only nutritious foods and you may be pleasantly surprised at how good you feel and how well you and Babykins will do.
Hope this helps,
D. S (mom to 5, granny to 2, CBE, doula, CLC)