Kekke, congratulations on the birth of your daughter !
I suspect you are going to get lots of responses to your post.
You are NOT failing your daughter, you are doing an amazing thing to BF under difficult circumstances, so be proud, not despondent!
No, BFing should not be sore. If is most likely that her latch is too shallow, ie she chomps on your nipple rather than breast. I was once told "It is called breastfeeding, not nipplefeeding, for a reason" and that is so true.
Have her lying tummy-to-mummy, either in a cradle hold or cross cradle hold; I find this more comfortable: you basically hold the baby's head with the hand on the other side of the breast you are using. She should latch on with a wide-open mouth, both lips kind of curled back, so it gives a 'fish mouth' appearance when she is on, she should take a good chunk of breast, more of the lower half or the aureaola than the upper part.
Look at these websites if you have the time, they have helped me A Lot. Dr Jack Newman has lots of videos that show you what a good latch/effective drinking looks like.
Initial latch-on should not be painful for more than the firts 2 or 3 sucks, if at all.
If you ask my opinion I would NOT add FF to the mixture at this point as it is v likely to interfere with your supply. Having said that, do what you have to, to survive .
A LLL leader once said to me "BFing is 10% technique and 90% confidence" and this is v true. Your body can do this, it is v early days, your milk has not come in yet, baby will want to and should BF v frequently at the moment.
Kellymom - evidence based BFing advice. Look at 'getting started'.
Dr Jack Newman - look at 'videos' and 'Bfing help'
V best of luck. You are doing great. Keep going. Can you get Lansiloh (sp?) nipple cream or an alternative?
Oh, and lastly, you are NOT failing. This is the v hardest of times, it will get better.