Sorry to hear your cycle was cancelled. I do know birth control pills can thin the lining. Estrace can help build the lining. They may start you on that after you start your af?
I am going through the same thing right now- did an ivf cycle and they had to freeze the embies since i got OHSS. now this cycle we started a FET but i have 4 cysts that are 20mm each and plus my lining is too thin so they cancelled my cycle. they had me on femara and said next month they may try clomid, but doesn't clomid make your lining even thinner? they didn't tell me to take BCP- they just said wait until my next cycle and we will try again. Should i be taking BCP?
Yes, they can certainly get worse... they can actually get so big that they burst and damage your ovaries, so it's no joke! I developed cysts after one of my IUIs and had to sit out a month with BCP, but they went away within a month with no trouble. Best wishes :)
The cysts are just the empty follies filled with fluid. They can go away on their own or you can take bcp's to help them go down. Most Re's won't do any treatments while you have a cyst because the hormones can make them grow and get worse. Because you have 4 of them it really is probably best to give your body a break for a month and rest before your fet. Best of luck - I am so sorry the first IVf did not work.