No! My LO's tongue is white and has been since birth but we've never had thrush. I thought it was just from milk. It's totally normal to feed all day, especially at only 12 days old! My DD1 fed all the time until she was about 3 months old! I think this is longer than most, but certainly the first month or so nearly all BF babies feed very often. He has to feed a lot to ensure you have a good supply of milk.
Tell her to bugger off, she doesn't know what she's talking about. My LO STILL has a white tongue for a while after feeds and he's 6 months old! As long as thers no patches that look raw when you rub them, or pain in your breast then it's unlikely to be thrush.
Check out LLL's info, it's always really good: http://www.llli.org/faq/thrush.html
And it's eprfectly normal for newborns to feed pretty much constantly for a while, you're doing amazing
He's your little boy, not the MIL's! We don't see apes and chimps timing feeds or flinging their young off after 15 minutes, baby and your body are in sync, baby has been used to a constant influx of calories and nutrients when in your womb, he's not used to this 'eat then stop' stuff, takes time . You have every right to ask the mil to leave, or just nod and smile then ignore her. Let her know you have access to proper advice, LLL offer a great support service too, and trust your body and your baby
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