Cause For Spotting Regularly?

Hello. I m 45 years old and still having the menstrual cycle normally its 2x a month about 2 weeks apart. Within the past year and 1/2 I was got off the depo shot because I wanted some normal hormones I had been getting the shot since for the past 17 years, so long because I m get migraines and thought it would help. My cycle is normally light and short lived, first one is crampy and heavy, second is light and spotty. My light and spotty started about 1 1/2 weeks ago and as of this morning it has not stopped which is unusual since it only last for about 3-4 days. I have become a little concerned on the regular spotting after so many days have passed.