your follicle size was perfect, but dear this is not the only factor for getting pregnant. the sperm should fertilize the egg, may be it didn't happen because the intercourse was not timed correctly, may be the sperm did not have enough energy, or just did not happen. on the other hand, may be the egg got fertilized but didn't really implant, so no pregnancy. see, there are many reasons, but also, this does not mean you can get pregnant, these follicles give you a higher chance. wish you luck in your next cycle.
BTW, try to do some test for your partner's fertility as well if this would help.
I agree totally with last post,just because of the sizes,it dont mean you will become pregnant,there are so many factors involved,im sure it will happen soo,dont loose hope.
sorry, typo, i don't mean to disappoint you. "this does not mean you can NOT get pregnant" and keep in mind that any healthy couples have around 30% chance every month to get pregnant. so, like said above. it will happen in time.