ABC News reports, that for more than a month, Donna Heller hadn’t been able to take more than a few bites of food without feeling uncomfortably full and needing to run to the bathroom. When she tried to sleep, she said it felt as if her stomach was “eating itself.”

Heller, a 54-year-old teacher from Crowley, Texas, was one of 400 people in 16 states and one city to become infected with cyclospora, a one-celled parasite that causes an intense stomach bug that can last more than a month. The outbreak has been tied to prepackaged salads in two states, but federal officials are still investigating.

“I had to wait three weeks to find out what was wrong,” she said. “It was very frustrating. I found myself in tears a lot of the time.”

Heller’s illness started on June 26 with symptoms typical of any other stomach bug: nausea, diarrhea, cramps and bloating. But unlike a stomach bug, it didn’t go away.

“I would feel like I was getting better, and it would come back,” Heller said. “You eat, and you’re right back where you started.”

She went to the doctor, who believed it was a virus and didn’t prescribe any medications. A few days later, she called her gastroenterologist, but he didn’t have any available appointments until Aug. 12. She called back three or four times, begging receptionists to fit her in, to no avail.

Then, Heller heard about the cyclospora outbreak and went to an urgent care clinic to get tested, but the results would take a while to come back.

At church the following Sunday, her family intervened and told her it was time to go to the emergency room.

“I told them [doctors] if you don’t give me an answer tonight, you’re going to see a grown woman cry,” Heller said. “I’m sure it wasn’t this way, but I felt like nobody cares that I’m this miserable.”

She said they didn’t test her for cyclospora again that night, and told her all her blood tests were negative. They put her on antibiotics, but she still didn’t get better.

A few days later, Heller got a call from the Centers for Disease Control and Prevention. She had tested positive for cyclospora and her results had been verified by the CDC. Doctors investigating the outbreak had questions for her: They wanted to know what she’d eaten. Although Heller ate mostly salads because she was on a diet, she’d eaten most of them at restaurants and didn’t know which one might have caused the illness.

The CDC doctor told Heller to take Bactrim to rid her body of the parasite, but it wasn’t the antibiotic she was already on, so Heller called the urgent care clinic. It didn’t believe that Bactrim was the right drug.

“The most frustrating part of all of this is I had to fight to get people to think I’m serious,” she said.

Finally, her doctor put her on the right antibiotic and she started to feel a little bit better. She hopes to improve enough to enjoy the last two weeks before school starts and she returns to teaching.

“Today is the first day I felt halfway normal,” she said.