Suggest Treatment For Irregular Periods,stomach Ache And Nausea

For the last 12 months about one out of two periods have been starting heavy then virtually stopping after 1-2days for about a day then resumming. It has happened this month and I have had quite bad stomach ache, not lower down as you would expect but around my belly button from left to right straight the way across, and feeling of nausea. I am 36 mother of 2 and am 99.9999% I could not be pregnant.