A new mother says a mix-up at a pharmacy led her to give her newborn daughter the wrong medication.

Brittni Mergl is blaming a prescription mix-up at a Bellport CVS for making her baby sick for two weeks.

She says she was supposed to be giving her 4-month-old daughter Erin medicine for acid reflux, but instead she had been giving her a steroid for two weeks.

During that time Mergl says Erin was vomiting, swollen, wouldn't sleep and was always crying.

"I put a lot of blame on myself," Mergl said. "But again, I'm not a medical professional. I don't know what I'm reading. I'm trusting that the pharmacy is giving me the right medicine. I'm sure everybody is trusting their pharmacy to get the right medicine."

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Mergl says the pharmacist was apologetic, but couldn't give her a full answer to how the mix-up occurred.

A spokesperson for CVS Health apologized to the Mergl family, telling News 12, "The health and well-being of our patients is our number one priority and we have comprehensive policies and procedures in place to ensure prescription safety. Prescription errors are a very rare occurrence, but if one does happen, we do everything we can to learn from it in order to continuously improve quality and patient safety."

CVS also issued Mergl a full refund for the wrong prescription and gave her the right prescription for free.

She hopes she can help raise awareness for people to check their medication. She says Erin is back to being her happy and healthy self.

After Mergl posted about the incident on Facebook, she says she learned that similar situations have happened to other people and with other pharmacies.

She is currently speaking with a lawyer about taking legal action against CVS.