Nursing makes periods so messed up. lol Mine was light some months and heavy the next.
eta- I even skipped a month once.
Breastfeeding makes my periods all over the place. I would get light periods or spotting some months. Sometimes I'd skip them altogether and then some months I'd get hit with super heavy periods. Since your on bc, i wouldn't worry so much, but I use to take a pregnancy test once a month just to make sure there weren't any surprises going on. :)