What Causes Irregular Brown Spotting Along With Cramps?

hi, i am 39 yrs old. I got my period last on Oct 15, I started to spot brown blood on the 29th. I thought nothing of it but it continued. I went to see a Doc on saturday. He told me it was normal sometimes and to call him back if it got heavier or painful. I am still bleeding but it is now red. Am I to assume it is now a normal period. I have some cramping. I had my tubes tied 4 yrs ago.