What Causes Heavy Irregular Periods?

I am 39 years old. i will be 40 in March. i am 5'8 and 132lbs. i have always been healthy. i have a 15yr. old and a 3 year old. i do smoke a pack everyother day. i started my cycle at the age of 14. i have always have had light period lasting 3 days. i have this month started period for second time. i had one 2 weeks ago. i have been bleeding for 6 days now and flowing and its been bright red. heavy flow. no cramping