Period length??

When I had irregular periods they use to last around 7 days... I had been on the depo for over a year and when I got off I was put on metformin (depo over 2 years ago/metformin last August) since I started metformin my periods have been 4 days long. Last month and this month they have went back to 6 days. I did start working out and lost 30 pounds since November and I quit my job and have stayed at home since middle Febuary... It's not really heavy or anything and the first day started late and was really light and the end days are the same way.. Almost stops closer to bed and then starts again. Nothing else has changed though.