Hey Stoked. Sorry your appointment brought more confusion than answers.
I did a real quick search of the literature. Some evidence to suggest it can help increase success of IVF (not very good evidence though)
But take a look at the abstract for this paper
Elsevier
It suggests that progesterone MIGHT help early on (to support the luteal phase) but after that it might just delay any potential miscarriages. That doesnt sound like fun.

Couldnt see any evidence of it causing any harm, but my guess would be that it would not really help at this stage. Personally, I wouldn't want to be mucking around with my hormones unless there was good evidence to support it. But thats just me. I can totally understand the feeling of just wanting to do SOMETHING to make sure baby sticks!!

It frustrates me how little research there is on it. In fact, there are more papers on progesterone supplementation in cows and sheep then there are for humans! I guess baby cows are worth more money