BBT & +OPK

Jenny • New Mommy to Jolie, Veterinarian and Husker Football Fanatic❤️
So like clockwork every month I seem to ovulate based on BBT, CM and OPK's on CD 15, (with a + OPK on CD 13).  This month my positive OPK's came a bit earlier at CD 11 (2:00pm) the neg on CD 13 (8 pm). My question is how soon after a positive OPK should I see a rise in BBT?  I normally get at least a full degree rise.  And is it true that little or no rise means no ovulation?   Sorry if this is confusing :(