I am 44. Periods always identical. 1st day light, 2nd day heavy ending day 4 or 5 with a bit of brown blood. Now 2nd month in a row periods changed.?

Keep a diary. This could be nothing. But for abnormal bleeding, I would recommend taking a pregnancy test and then keeping a menstrual diary. Take this information to your physician and they can help make a plan for you. There are many causes for this, but what you describe can be normal for periods to vary.