Uterus Biopsy

I started a new cycle so I can get a uterus biopsy so we can pin point the transfer date better.  My 1st transfer was unsuccessful..  The Dr didn't know why because our embryos were perfect...  My uterus lining was perfect,  and the transfer went normal..  So they are thinking that I in a small percentage of women that need an exact date of transfer so we will be trying this..  I'm scared to do another transfer and it not be successful...  Please keep us in prayer...