Hi Janine
the reason I ask is that I had similar experience.
I was fine until I lost some weight then a month or 2 into my diet another period started after a long gap.
Seems to be down to estrogen stored in our fat, just my theory anyway.
Since then I've moved to HRT and things have settled very well.
However some of the symptoms took 6 months+ to settle.
Hope you find something to help you soon.