It is a little hard to provide you with direction because your question doesn't have much information in it. For example, how long are your periods normally? If they are typically seven days long and this time one three days, that would be significant. On the other hand, if your periods tend to be quite irregular in timing or in length, then a light three day period might mean nothing at all.
Because of this, probably the best thing to do would be to call your regular primary care doctor
or your OB GYN doctor about the issue and ask them what they think. Since they know your case best, they should be able to provide you with more definitive advice.
For example, sometimes depending on the timing of the bleeding
, an event like this might represent a pregnancy or an early miscarriage. On the other hand, in the right context, it might be a sign of polycystic ovarian syndrome, or some other condition causing irregularities in the hormone cycles associated with menstruation.
Your doctor will have a lot of additional questions for you, and they will also perform a physical exam. Based on these, they will be able to give you advice.