Irregular periods?

Looking for advice here because my mom couldn’t answer me really.

I have like 2-3 weeks between periods but sometimes it’s 4-5 instead. And also it can be 4 days or 8 days. Sometimes it’s a ton of blood and sometimes it’s not much. And every once in a blue moon I get cramps so bad I have to go home from school because I can’t walk or even think even on meds. Other times there’s no pain at all.

Im on day 8 rn and flow is light/medium but slightly worried at how long this is dragging out. And also the period before this one had ended two weeks before this one started so... I’m tired of bleeding so often I guess? Is this normal? I’m not sexually active and I don’t practice masturbation, and I haven’t had any symptoms of infection or anything.

Im 18 and kind of ignorant when it comes to this so. Any help would be appreciated. Should I talk to a doctor or is it fine?