When I took bio, i also learned that progesterone was the negative feedback, but in my Kaplan classes, and from what it says there- esp if you're getting a question from them, they say that this is what happens:
fsh is increased to make follicle- fsh secretes estrogen
Estrogen increases, and eventually shuts off Fsh and LH gets turned on (also by estrogen) , and by turning on LH, you get the follicle to turn into the corpus luteum, which secretes progesterone to mature the endometrium for implantation.