Many thanks for your comments.
My diet has changed I eat more fruit and veg, yoghurt and cheese. I have read dairy products can cause this, maybe it will be a process of elimination.
I also wondered about vaginal tears as it only happens once intercourse has started.
Its quite frustrating when my Gyne says all is fine!
I read that vaginal tears are more common in women who are post menopausal. Its possible he tore you inside, and a channel has formed into your rectum?
What are you eating now? is it anything different than before? this also effects what it tastes like (from an oral sex point of view)