OKLAHOMA CITY - Viruses exist all around us, but we depend on our immune system to fight them off.

However, imagine if your immune system didn't do that and you got sick at every turn. That's what happened to one Oklahoma teenager, who spent much of his childhood with no immunity.

Matthew Gilbert, 15, doesn't take anything for granted. That's because at one time, something as normal as going to school, surrounded by friends, was taken away from him.

"You just kind of learn to push through it," he said.

On the outside he powered through school and karate, while on the inside, he fought one virus after another.

"Me and my mom call it feeling blah, it's just your entire body is drained of energy," Gilbert said. "You just feel like your melting."

His mother, Deana Gilbert, soon noticed a pattern.

"Any time we were around a big crowd of people, it seemed he would catch something crazy a virus or have a sinus infection," she said. "He was on one antibiotic after the next."

Multiple doctors later, the family still didn't have a diagnosis for Matthew, because many believed he would simply grow out of it, until he hit third grade.

"It got worse," Deana Gilbert remembers.

He had to leave school and karate.

"It was affecting everything, joints, he was in pain, he was tired and had pneumonia at the time," she said.

Home-bound and homeschooled, Deana Gilbert kept Matthew isolate from the outside.

"That was very difficult at first," Matthew said. "But that's how I got into computers because I could talk to with my friends and still play with them but not have to be physically next to them."

Finally at age 10, he was diagnosed with CVID, Common Variable Immunodeficiency, a disorder that affects his immune system. However, Matthew took 11 different antibiotics and nothing worked. Then, he met Immunologist Dr. Amy Darter at the Oklahoma Institute of Allergy & Asthma (OIAA).

"I basically took him from a weekly therapy to a bimonthly therapy," Darter said.

She also increased his dose of hizentra, a treatment injected under the skin that's full of antibodies. He gives himself the treatment from home.

"I'm able to go a solid week and a half without feeling down and that is just incredible for me because I'm able to do a lot more than I was before," Matthew said.

He's also back in school with his friends at Yukon High School.

"Luckily with Matthew, we've got him early enough and got him under good control and he's doing quite well," said Darter.

And his mother, while still cautious is able to let go a little.

"As a parent you just don't let your guard down but you can't hold them back from living their life," she said.

Deana Gilbert says the earlier you diagnose, it could saves organs. Meanwhile, Matthew wants to start a walk to help patients fund infusions.