I had my period on September 26, 2018. In November, I experienced bleeding for three days, but later started to lactate. Is it possible that I could be pregnant?

Usually lactation won't begin until the end of the 3rd trimester or after the baby is born. It could be mastitis or a problem with the mammary glands. I suggest you see a doctor to ensure everything is okay. You may be pregnant...but what your experiencing isn't necessarily a sign of pregnancy.