Irregular periods?

So I usually have these super heavy periods where I bleed heavily for 5-6 days. The last 2-3 cycles I've had, there's either been only a day or two of light bleeding with about 2 weeks of spotting or just spitting for up to 3 weeks with extremely light bleeding occasionally. Anyone know what could be causing this?? I've scheduled an appointment with my gynecologist but it's not for another month.