breast fed ds on demand until about 8 weeks, hungry baby, 92% percentile, always fed well etc
introduced bottle of formula 7 and 10 pm, been fine for a month or so.
implemented loose routine, basically trying to encourage 3 hourly - went ok for a couple of weeks.
DS continued to put weight on same curve, ie) heavy 
Now suddenly this last week breast feeding has gone "wrong", cries, pulls on, off, cries, looks angry, milk is there I can see it coming out.
Today close to giving up as he kept crying (have stroppy 2.5 year old screaming at me about breastfeeding too) and gave him a bottle which he slurped happily.
Am not anti formula nor massively pro breastfeeding. In another month or two would like to switch anyway so what to do for now ....
Why is my 13 week old suddenly unhappy to breastfeed? he seems in pain doing it? teeth?