Changes in menstrual cycles

I have been having issues with my cycles. They are 28 days which normal.however my period is lasting 10-12 days. The first 7 days pretty much normal for me but then this is the strange part. Around day 8 when it appears it might be over, no bleeding for half or more of the day, it starts again with a vengeance. It's heavy but not to point where I am too worried yet. But the pain is unbearable. I never used to get period cramps. So Doctor today is wondering if I have endemetreosis, if I spelled that right. Doesn't want me to start a birth control pill, I have been tapering for a year now and have had so many of the symptoms mentioned on this forum,so he hates to add another pill to mix if can be avoided. I am 42 and according to blood work not in peri menopause. So was wondering if anyone else have similar issue. Is this just part of withdrawal and will hopefully correct itself. Any insight would be appreciated. Thanks. Hang in there everyone!