Don't be worried
In early pregnancy it is not necessary to get any weight. The amount of weight you should gain will depend on your size before pregnancy and your body type. Healthcare provider generally recommend gaining 20-30lbs during your entire pregnancy. More than 30lbs of weight gain increases your risk of complications during the last trimester and during labor and delivery.
Early in your pregnancy discuss your current weight with your doctor and ask them to let you know how much weight they would ideally like to see you gain during each month of your pregnancy. At any point if you are concerned talk to your doctor. Make sure you are eating a healthy diet and having normal exercise and you should be fine.