It could be that your heavy days have gotten heavier. Or it could be that your cervix has gotten danglier, taking up room where flow should go (perfectly normal.)

Compare the dimensions and capacity of the cups you have to other brands using http://sizecharts.livejournal.com/ or any of the other charts found online. You might want a higher capacity cup for your heavy days.

I'd probably went for a medical check-up to see if everything is alright down there.

Edited at 2016-07-30 12:43 pm (UTC)

A little variation is normal but a lot could be a sign that something is amiss -- especially if your months alternate heavy and light. You probably don't need to make a special appointment but it's something you might want to mention next time you go to your doctor.

The good thing about cups is that they can be used to measure flow. If your cups don't have measuring lines (I think your Lunette has subtle markings) then put in 10, 20, 30 ml of water. (Or use teaspoons or tablespoons as measurements.) And then keep track of how much is in your cup each time you empty it. Tally it up at the end of the day and write it on a calendar or something. That's really good quantitative information to give your doctor.

Keep track for a few months to see if you really are having surges or if it just seems that way.

From anecdotal evidence here, the most common cause of variable or heavy bleeding seems to be fibroids. They're more of a PITA than a problem -- but they could cause difficulties if/when you decide to have children.