I'll be very interested to see if any one responds, I feel your pain! Although mine is not just about PMS, it's also pre-ovulation, post-ovulation, and post-menstruation. So generally I get about 3 nice days in a row MAX before the next part of my cycle sends me into a rage, or a weep-fest.
When I talked to my Ob/GYN, he said the same thing, even after I told him I never take BCP since my breast cancer was hormone-receptor positive, I will never take hormones. And he was like "well, not forever, just to see if it makes a difference..." Argh.
I did see an alternative medicine RN who tested my hormones over the course of a few days via saliva tests. I'm not sure how thorough that it, but she claimed they were basically within the normal range. She talked a lot about nutrition and supplements and gave me handouts about foods that should be avoided and things that may help. I haven't found much success there but it's completely due to my own inability to pay attention to it and change my cooking habits, as I find it overwhelming and hard.
A couple years ago I was easing myself off Lexapro and used a supplement kit I found online. There were several different mixtures that had a variety things in them (vitamins and herbs) in different combinations, used at different times in varying quantities. Clearly I should have kept better track of what I took and when, because looking back I do think that my moods were more stable then than ever since. Makes me think I would like to try and see if similar things exist for monthly hormone fluctuations.
Very generally speaking, I find a lot of relief from tracking my days and anticipating them. If I know that tomorrow is day 18, I plan accordingly: make a simple dinner, clean the house today, make sure I get some exercise in early. Trying to avoid the stress I know will set me off, make myself feel good on that day, and make sure I don't attempt to tackle any big issues in that mood. It can wait until the chemicals pass.