I used viagra with my last cycle, but I'm not really sure if it helped as I tried so many things. However, I read online that you have to use the suppositories as the little blue pill simply doesn't work vaginally (I actually tried the pill orally one cycle and was canceled due to poor lining). I took 25mg 4x day. It's important to stop when you start PIO.
I would also try estradiol injections. I'm sorry you have to deal with this, I know how frustrating it can be.