Hi Elisabeth!
Lots of folks here gained weight with pregnancies, and with kids at home, it is harder to start on the path toward getting healthier. The good news? Making a healthy foundation for your family now, including healthy eating habits and regular exercise, is going to have immense benefits in the future not only for you, but also for your son, who will have good habits in place before he even realizes what you're doing!
Have you visited our 20-somethings forum yet? What sort of plan are you following? We have forums for most healthy ways of eating, so look around, find a spot, and settle in.
Can't wait to hear more from you soon!