D.D.
I was exactly in your shoes L., 30 is not old by any means, I am 46 now, but had my son at 30 and only gained 20 lbs but gained it back after delivery! I looked better at 3 months after delivery than I did a year and a half after delivery! The best thing to do is get that metabolism fired up and that usualloy means doing some type of weights (building muscle) and a bit of cardio. Pushing the baby in the stroller at the mall, or walking or light jogging. you are still very young! Dont think of youself as older.
Also, it does seem that our bodies hold onto carbs and sugars much easier than they did in our 20s and before baby came along. Wieght watchers has a great program, you can do online. By eating mostly protien and green veggies you can loose up to 1 lb a day! (LEAN AND GREEN)
Avoid bread, pasta, rice Cokes, etc. Lean meat and veggies and it always works for me. Wish you luck! And hope you have a great 2nd preganncy! You are still a Spring Chicken!