myturn, like some above, I'm in the 3-digit range for weight as well and, even in that range, if it's contributing to my IF, it's like a raindrop contributing to an ocean... If you were "unexplained", maybe you'd take a close look at it being a suspect, but you'd probably be seeing hormone imbalances and other obvious signs of the weight playing a part... I have one friend who probably was only IF because of her weight and there were clear signs suggesting that was the case - she simply didn't respond to the FSH injections (after a full month of daily FSH injections she had no follicles over 14mm) and had long annov cycles even though she didn't have PCOS - she lost weight and got pg without medical assistance (twice!) and when she got her first BFP she was still up around 120kg (after losing weight). If losing weight will make you feel better, then, by all means, work on it, but do it for yourself, but don't use your weight to blame yourself for your BFN. The BFN is not your fault, hun. You did all you could and were unlucky; you did nothing wrong.

As for how long to do this, that's different for everyone. At some point, the pain of continuing outweighs the pain of stopping... Until then, we keep putting one foot in front of the other and soldiering on...