Everything changed on July 23 when he called his mother in pain.
"First he said, 'I am going to the hospital because I have a stomachache. I can't drink water, I can't eat anything. I'm just throwing up and I have diarrhea,'" his mother said to WFAA-TV.
At first his doctors in the Rio Grande Valley thought he had pneumonia, but none of the traditional treatments worked. So he was flown to Baylor Hospital here in Dallas a month ago.
"You know this was a mystery for them, and the doctors decided they were going to put him on life support that filters your blood," his mother said.
Hernandez's mother now says doctors believe all of his troubles began when he started vaping about six months ago. The day before he fell ill, he had vaped with THC.
"From a mom's perspective it's very painful. It's very hurtful to see your child in so much pain and not be able to help them," his mother said.
Hernandez was able to talk to his mother just before he was put on a respirator.
"He was scared of not being able to breathe. He didn't know what the outcome or what was going on with him. He said, 'Mama, I'm scared'. I'm scared -- that that's all I can hear him saying," she said.
While Hernandez struggles to live, his wife gave life to their third child at Baylor Hospital in Dallas.
There have been reports across the country of people suddenly getting sick after vaping. Hernandez's mother says that's why she decided to be a voice for her son.
"And I know right now if he was here speaking right now, he would warn everybody right now to stop," his mother said.
She says doctors don't think there is much more they can do for Hernandez, and they may have to make a difficult decision to take him off life support. But for now, they pray for a miracle.