From the experiences of my sisters & friends, I've learned that 15lbs is the average weight Drs recommend you gain during pregnancy. You do need to feed yourself as well as the baby but you can still be mindful of what & how much you're putting into your body. I don't know about your gym situation, but at most gyms & in some communities there are exercise classes designed for pregnant women so that you are still getting adequate physical activity but not over doing it for baby. First & foremost you need to talk to your doctor about these things.