I'm the same (ish) technically if going by my normal cycles I'm due anything from tomorrow until 14th, but came on late due to stress in May so was the 18th.
But I am still getting BFN's.
Ill use my FRER about 2-3 days before period would be due as I can't afford to see a BFN haha, FRER are £8 for 2 where Internet cheapies only a fraction of that!