Periods getting heavy again with mirena coil?

[Libertyl]

Hi, I am new here!

I have been using the mirena for 5 months now to treat my Endometriosis, which i had removed with laparoscopy in January.

At first my periods were light with the mirena pink in colour, still very painful, but light bleeding.

However this month it has been quite heavy with clots, which I just find strange since it was light before, any idea why?

thanks

Liberty