Lindsey Bliss, from New York, US, said she was suffering full body shakes as well as a “crushing” headache due to mastitis.
“When a good boob goes bad - again,” Bliss wrote in the Instagram caption on Sunday 5 March.
“I literally wanted Dan [her partner] to bring me to the emergency room last night due to the most epic engorged boob. On the mend today from my bed. Why does this keep happening?”
Bliss shared the hashtags #redboob, #goodboobgonebad and #breastfeedingisnotalwaysmagical alongside the snap.
It’s clear in the photo that the mum’s breast is red and sore, but carrying on breastfeeding is exactly what she should be doing, according to Royal College of Midwives’ (RCM) professional policy advisor, Sarah Fox.
Fox told The Huffington Post UK mastitis is not unusual for mums, even those who are successful with breastfeeding.
“The most important thing to do is to not stop feeding,” she explained. “Mastitis is where you have a small blockage of milk ducts that causes your breasts to be sore and can make you feel unwell.
“The best way to release the blockage is to keep feeding, even if it is sore. Women can also gently massage their breast to help get the milk moving down the ducts more freely.”
Fox explained that historically, women were told to stop breastfeeding if they had engorged breasts, but she said that is the “most unhelpful” thing to do.
She advised women to take paracetamol to help with discomfort and pain and encouraged them to drink lots and keep feeding.
“If it stays for a couple of feeds, it’s not relieving itself, you’re feeling worse and your baby is unsettled, we would encourage you to seek support from your midwife or GP,” Fox added.
“But what we don’t want is for a woman to feel alone or feel less like she wants to carry on breastfeeding, so we always welcome any women to share their experiences or ask for support.”
Fox added that it’s unusual to have repeated episodes of mastitis so if this happens, seek professional help.
She concluded: “The best thing for any woman suffering is to have your baby emptying that breast.”
For more information on mastitis, visit NHS Choices.