I began giving both of my sons a bottle at night just so I could have a chance for my boobs to 'refill' smile The evening seemed to be when they were hungriest and my boobs couldn't keep up. Apart from that one bottle, I breast fed DS1 until he was 1year old - then he lost interest! DS2 is only 3 1/2 months and I'll probably do the same with him.
Are you sure that your little one is definately hungry or is she unsettled for some other reason? Overtired maybe? I made the mistake of trying to feed DS1 all the time when he cried because I thought he was hungry (First time mum, I was worried he was starving!) I found out from the paediatrition that I was probably feeding him too much and he was getting a stomach ache!! sad When I stretched his feeds out eventually to four hours, he slept better and was less grizzly! How was I supposed to know - I just assumed that he was hungry everytime he cried - and everyone around would always say 'oh, he MUST be hungry'!!!!!!! >:-< so I would feed him!! When really he was probably just tired!!
I still had more than enough milk with DS1 and I still wake up with massive boobs full of milk now even after 3 1/2 months - and that's with a bottle of formula thrown in. As for the sore nipples - hang in there, it gets better, just make sure that bubs is attached properly.
Good luck with it all - let us know how you go! smile !