What Causes Heavy Menstruation With Pain And More Frequency?

I am 45 years of age. I have been having heavy and more frequency monthly cycles for the past year. But the last two cycles have been very painful on the left side, the pain is debilitating, i feel sick have no strength and feel very unwell. I am quite worried about this as i have not suffered with at all since my cycles started at age twelve. Could there be something wrong, or is this normal for my age.