)) You're not crazy, and CONGRATULATIONS!
I, too, started thinking about FET's compatibility with breastfeeding very soon after I delivered my son. I have been breastfeeding him for 10.5 months now, and I'm waiting for AF to call the clinic and launch an FET cycle. When I do, I'll wane him completely.
Months ago, I talked to the clinic's nurses, doctors, and pharmacist about FET meds and breastfeeding. Because Suprefact is used in the protocol, they told me it's 100% sure I have to stop breastfeeding before I start taking it. Superfact and Lupron are mostly used for prostate cancer... so there's little to no research on pregnant/nursing moms.
But the pharmacist also did some research to check for the other meds - estrogen and progesterone. They're pretty much at ease with the progesterone intake, because we also take it all the way through the first trimester. However, they're far less sure about estrogen. I'll take Estrace (pills), and the pharmacist couldn't find a clear indication on the matter. Namely because, like so many FET-IVF meds, there's almost no research with pregnant or nursing mothers. The doctors at my clinic want to play it safe anyway, and so did my pharmacist. They all told me that, due to the lack of research on all those meds, I had to wane my son before attempting FET again, just to play it safe.
Hope that helps,