Period changing the older I get

[Catscat]

I'm 29 and my periods have changed.
First day will be heavy, Ill soak through a few tampons throughout the day and at night a thick panty liner is needed.,
Then day 2 I can get away with 3 tampons and and night I can get away with nothing just black undies.
Day 3 I will need 1 tampon and the blood is very dark brown .
Day 4 just thin panty liners.
A pack of pads will last me at least 6 months...
My periods never used to be like that

What could it be

Mine have become similar to yours OP, I'm similar age to you too (31). I'm not sure if it may be related to my contraceptive patch.... I'm a bit rubbish at tracking them properly but they're aren't as predictable as they used to be