My understanding of saddle-fitting is that you can't really be between sizes - if your sitbone measurement is wider than what will fit on a 143 saddle, then you really need to be on a 155 saddle. So the girly-bits pain that you're having may be b/c the narrower saddles don't support your sit bones properly, leaving all your weight on the soft tissue. This is also why you're not having sit bones pain on the narrower saddles - your sit bones are not really ON the saddle! You should try a saddle in the 155 measurement with a bit more padding and see how that pans out. I ride a Specialized Ariel (it's a mountain saddle but looks great on my road bike). It's definitely got more padding than the Lithia and comes in 155. That might be a good option for you to try.