Severe PMS only every-other month?

I am a 26 year old female, diagnosed with Polycystic Ovaries at age 16. For the past 10 years my periods have been regular (monthly) through the use of metformin, birth control pills, or both. Currently I am only on metformin and have not been on BC for about 2 years.  I've gone from 273 to 180 lbs now and yes, my periods seem to be more regular than ever, in case that helps.

I have nearly always had severe PMS symptoms, enough to classify as PMDD so I tried the birth control Yaz for that and also added in 10mg of prozac for the 2 weeks before my cycle. Neither really made a noticeable difference over months and years.

What has been happening for a while now is that every other month I will have severe symptoms, most notably extreme cramps and all over body pain and incredibly horrible mood swings. Like the type of mood swings you would expect from someone with bipolar disorder which I do not have. On the alternate months, I have only mild PMS symptoms like being slightly emotional and a little bit of cramping. I have a cycle every month but only every-other month is the severe symptoms.

What I'm wondering is WHY? Does this mean one of my ovaries is releasing way more hormones than the other so I only feel this way on the month it's working? Has anyone else experienced this? Anyone have a suggestion for how to help it?