I questioned this with my GP last week, I have about a 12 day LP... she said that as long as you are ovulating, that that time frame is enough time! So I think 11 days would be okay for you, any less and it might be a concern.
So many factors can contribute to the length of our cycles - I've said it before, but for 20 years my cycles were religiously 28 days with O on day 14 - now, when we are TTC they are about 32 days with O around day 20-22 - this cycle O is two days earlier than last, sigh! Haha... So frustrating!
Could you have Oed earlier than you thought?