Lionfish, I was also diagnosed "unexplained". I've done a few ivf cycles with one early m/c.
February I did a fet cycle which was unsuccessful so I decided to see a naturopath until I was ready to go back for stim #4. I started seeing her in April and last week I got a BFP. After doing some charting, she felt that I o'd too late and that my eggs would not be good quality at around day 20 when it was happening. She put me on some herbs to move O back (which it did straight away to day 17), and my 2nd month ovulating at day 17 and we have a BFP!! We have never been pregnant naturally, so it was a complete surprise.
I have always ovulated late, but the Dr's only ever tested to make sure that I ovulated, not when and obviously not the quality of my eggs when I O'd naturally.