Irregularly long (and light?) period

Help pleaseeeee! I am currently on day 9 of my period and I feel like somethings up. My period is always consistent, like clockwork, 4-5 days and fairly heavy. I usually go through 5-6 tampons a day. But then With this period it has been so light that a thin pad lasts all day. And I’m now on day 9. No changes in diet, no changes in stress levels...what the hell😂 thanks in advance!