Period cycle still irregular after 9 years

So i got my period when I was 12 and now im 21 and the cycle is still inconsistent. You would think it would have a pattern by now but no it still shows up randomly every time with a mind of its own and surprises me. Which sucks cuz I can never see it coming and never know when to expect it. My shortest cycle has been 24 days and longest was 39 days but typically I guess it averages around 27-35 days.

But I always have to just wear black pants and stay cautious for like 2 weeks every month for it to show up any day during that time frame. Anyone else similar??? Or know anything about this?