Kelly, my SIL had her second baby late April, and started the TF early June.
She did call them before she started in regards to BF, and they said they would let her do it, but weren't happy about it.

She did much tossing and turning, and decided to go ahead anyway - If it started to affect her milk, she was happy to stop.
She's still going now, and baby Alex is by no means suffering... she is thriving.

SIL also found in the TF booklet at the bottom of one of the pages that for people wishing to do TF whilst lactating, this was fine, just to add an extra 500cal a day to make up for what you're burning BF. ( I looked through and found this too - but in my booklet its on the maintenance page... on hers, its in the first section. She was on TF before she fell pg with Alex, though, so her book is a little over 12 months old. They've obviously changed their views.)

SIL has decided to keep doing it - but isn't completely strict, and has been adding the calories accordingly... following more the maintenance plan, although she still has the 2 shakes a day.
Since beginning in June, she's lost 9kgs.. thats great for someone not following it strictly, too.

Good Luck with what you decide to do - Such a bummer because you were off to a great start!

Whatever you decide - Don't feel like you're a terrible mother... OMG there could be worse situations than this one!!

Love Holly
xxx