Thin lining during FET cycle

Marissa
I'm currently on my 2nd attempt at a frozen embryo transfer. My 1st attempt was in September and it was cancelled because my lining wasn't getting thick enough. At that time I was taking the Estrace pills orally and then vaginally. 
This time I'm taking the Estradiol patches and now one Estrace pill vaginally. At my last scan this past Tuesday, I was CD 11 and my lining only measured 5.9. I'm worried that this cycle will also be cancelled. Why is this happening to me? Is it possible that my lining will never get where it needs to be? I have pcos, is that why my lining is thin?
My next scan is this Tuesday. I did acupuncture for the 1st time yesterday, hoping that helps.
Does anyone have any experience or input regarding this? I'm so worried. :(