You can actually get plant derived progesterone as an over the counter cream if thats's something you'd like to try. I don't think this counts as self medicating since progesterone is not known to be dangerous and you can legally buy it without a prescription. Your endo might be upset if you take it without telling them though.
I've been using the Emerta progesterone cream for several months now, and I noticed some real effects from it. Just not the ones I was looking for.

It did increase my energy levels somewhat, which was a positive effect. But it also increased my libido, which is not something I necessarily want to deal with still being pre-op. It was interesting though, because like Kate, it pretty much only increased my attraction to men, even though I identify as bisexual. I've been starting to think lately that even if I am fine with dating someone of either gender in principal, actually dating another girl wouldn't work very well for reasons of sexual compatibility...
I decided to stick it out and see if there were positive physical effects, but so far that has been disappointing too. My breast growth has been stalled for a while now, and adding progesterone didn't seem to make much of a difference. I wonder if it would have helped more if I'd been taking it earlier on while my breasts were growing more actively, but I guess it's too late for that now.

The good news is that I decided to start cycling the cream for a while to see if that made any difference, and once I stopped using it I started to feel some soreness in my breasts again. I think they might have grown a little since then, but it's hard to tell. I've heard the theory that one of the reasons progesterone can help with breast growth is that it actually competes with estrogen, which can act as a reset switch to keep your breast tissue from getting "used to" your estrogen levels, so that is why it's important to cycle. I was skeptical about that though, since women tend to experience a spurt of breast growth during pregnancy when progesterone levels are consistently high. Anyway, I am going to keep cycling for a while to see if it makes a difference.