Don't worry. I've had this before, it's normal to have some periods close together. If this happens every month it may be good to research. But if it's not often it's fine.
There are many possible conditions that can affect your menstrual cycle. Several complaint has been reported(2 period in a month) due to contraceptive intake. I will recommend that you should contact your doctor or get over the counter pregnancy test kit to be sure of yourself. Lighter flow you had is called Spotting. Spotting is light bleeding from your vagina It's similar to a normal period, but much more lighter. The color of the blood can be anything from red to brown. In early weeks of pregnancy, a little spotting or bleeding is common.