personally my experience with prog. cream sucked (and i took it the way all the online directions say for low progesterone)
I always get breast pain on either the sides/nipples and/or the tops of my breasts, sometimes both in the same cycle (during tww) so I think that the where it's happening diagnosis is pretty much a load of bull.
However since you keep getting chemical pregnancies (and not just evap lines that get your hopes up) you could try it out, I personally thoroughly enjoyed my first bottle I bought which was source naturals natural progesterone cream.
Make sure to get natural progesterone and not progestins...
and this video explains very well how to apply it:http://www.youtube.com/watch?v=3KZ__Vx4TVw
And if you use it, do NOT get your hopes up over high temps or any other pregnancy sign unless you get a BFP because the month I used it I had no risk of pregnancy but had every pregnancy sign in the book short of milk production.