Irregular!!

I've always had painful periods - recently (10 months or so) they became super irregular. I never skip one, the bleed is never heavier (lighter maybe) and the pain hasn't changed, but it worries and frustrates me that I can't predict them!!
In the last 4 months I've had seven separate bleeding incidents, all similar in length (a few days) and flow so it can't just be spotting. 
I've been to my GP three times, the last time I finally got a blood test, which came back excellent. No hormone imbalance they tested for, thyroid, liver, kidneys all fine. 
I went to the sex clinic just in case (although I've had one partner for three years now) but that was all 👌 
I had an ultrasound which showed nothing but the fact that one of my ovaries is a little larger than the other which apparently means nothing!!
And yet it still comes and goes at it pleases! Had one two weeks ago for about 3 days, just started another now. 
Has anyone else experienced this, am I just super unlucky?? Help!!