I would go straight to IVF if your FSH is elevated. I wish I had skipped my third iui and gone to IVF. My FSH jumped from 8.9 to 11.7 in two months and my astral follicle count went from 14 to 9 in two months (and then to 7 two months after that). If anyone had told me things could change so suddenly, I would've skipped the last iui and jumped to IVF.
Good luck !