Small Uterus - Hypothalamic Amenorrhea

Hi Dr. Elaine Brown,

I was diagnosed with primary hypothalamic amenorrhea.  I've never had a period of my own (only with bcp).  I'm on my 2ww after a 2nd IUI.  My luteal phase was 14 days on the first cycle which resulted in a BFN.  My uterus lining this time was 7mm and 2 follicles on each side at 18 and 17mm on the day of Ovidrel.  

I have a smaller than normal uterus and am really worried.  Every ultrasound technician makes a comment on its size.  My RE doesn't seem to be concerened at all b/c I can get the periods with the pill and my lining is reponding to treatments.  He said the uterus is made for stretching and not to worry.  Do you have any thoughts on this?

Thanks!