Thanks for the query.
Some amount of irregularity in menstrual flow can be seen during perimenopausal period.
According to your description there is more possibility for hormonal
Anyhow better to get examined once.
Consult gynecologist, get examined and go for ultrasound
With this the possible cause can be made out and treatment can be given accordingly.
Better to stop smoking
or at-least decease the number.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429