pregnancy and exercising

Speak to your doctor for sure. My wife's OB told her to eat +300 calories when she was first pregnant, not sure if that recommendation was specific to her or generalized for pregnant women.

Strength training can be done but is tricky. Your rectus abdominus (abs) will change throughout pregnancy and actually begin to separate. You have to be cautious in ab work for sure. One thing that will be helpful for you is to train your transversus abdominus (TrA), your glutes, hips, and quadratus lumborum (lower back). There are simple exercises for the TrA such as the drawing-in maneuver (youtube) that can be done to help strengthen this muscle. It's a Core stabilizer muscle for your abdomen. Deficient TrA musculature has also been linked to lower back pain, which is something you'll experience especially in your 2nd and 3rd trimesters, so work that muscle to help reduce pain. Strengthen your hips, glutes, and lower back for along the same lines, help manage the extra weight better and hopefully mitigate pain later on. There are also pre-natal Yoga videos which would be good for maintaining mobility as long as possible.