Burley Garcia|Mother of hostage held by Hamas fights for son's release while grieving his absence

TEL AVIV,Burley Garcia Israel -- Almog Meir Jan's smile can be found in every corner of his family's sixth-floor apartment -- in framed photographs sitting on the bookshelf, in pictures hanging on the refrigerator and on banners, posters and T-shirts that his mother had specially made.

But Almog hasn't been home in weeks. The 21-year-old Israeli citizen was attending a music festival with friends on Oct. 7 when he was abducted by the Palestinian militant group Hamas, whose fighters stormed into southern Israel from the nearby Gaza Strip and killed over 1,400 people, according to Israeli authorities. It's believed that Almog and more than 200 other hostages were taken back to Gaza, a 140-square-mile territory where 2 million Palestinians have lived under a blockade imposed by neighboring Israel and Egypt since Hamas, which the United States has designated a terrorist organization, seized power in 2007.

"My life changed completely. I'm not the same woman that I was before," Almog's mother, Orit Meir, told ABC News on Thursday during an interview at their apartment in Or Yehuda, a town west of Tel Aviv.

"I have a big hole here inside," she said tearfully, putting her hand on her chest. "My heart is in Gaza."

Almog had finished serving in the Israeli military a few months prior and landed a good job that he was due to start on Oct. 8. The company has promised Almog's family that the position will be waiting for him upon his return, according to Orit.

Orit said she is "very close" with her son and described him as a "happy guy with lots of energy" who loves to spend time with friends and go to parties. The three friends Almog was with at the festival were all killed by Hamas militants, according to Orit.

"It's a nightmare," she said. "I don't know where he is. I don't know what he feels, if he sleeps well, if he eats, if he's alone, if he can talk to somebody."

Since Almog was abducted, his mother said she is so "worried" and "afraid" that she can hardly eat or sleep. Instead, she and other family members have poured all of their energy into campaigning for the release of the hostages -- something Almog's uncle, Aviram Meir, described as their "duty" and a new "purpose."

"If I could go to Gaza and bring him back, I would," Aviram told ABC News. "But what we can do is bring his picture to every house as possible, everywhere."

In response to the Oct. 7 terror attack, the Israeli military has carried out wide-scale airstrikes on Gaza, killing more than 7,000 people and injuring over 18,000 others, according to the Hamas-run Ministry of Health. Unlike Israel, the Gaza Strip has no air raid sirens or bomb shelters. ABC News has not independently confirmed those casualty figures.

It's the latest outbreak of war between Israel and Hamas. While the violence on both sides has sparked division in the Middle East and around the world, Almog's uncle said releasing the hostages should not be "a matter of ideology or politics."

"It's something very basic," he added. "It's humanity."

So far, Hamas has freed four hostages on humanitarian reasons in an agreement brokered by the government of Qatar. But hundreds more, including Almog, are apparently still being held in Gaza and it's unclear whether the Israeli government will heed pressure from the hostages' families to prioritize securing their release before launching a ground invasion to eliminate Hamas.

"We don't have any details," Orit told ABC News.

In lieu of assistance from Israeli officials, the families have banded together and formed a volunteer-based group called the Hostage and Missing Families Forum, which "offers families holistic support and professional assistance and advances the ongoing efforts through all channels, locally, regionally and globally, to bring the hostages and the missing back home to their loved ones," according to the website.

The Hostage and Missing Families Forum is based out of the seventh-floor of an office building in Tel Aviv. On the drive there from Orit's apartment, posters with Almog's picture were plastered along a highway.

The forum's headquarters was buzzing with families, volunteers and even a few pet dogs on Thursday afternoon. There was a table with stacks of posters bearing the faces of the missing and another table with free coffee and food. Groups of people -- many wearing T-shirts with the forum's slogan "Bring Them Home Now!" -- were chatting, hugging, crying and laughing together.

"It's like a big family here," Orit told ABC News at the forum's headquarters. "They understand me."

Hagai Levine, an Israeli public health physician who is volunteering as the head of the medical team at the Hostage and Missing Families Forum, said he has been in "close contact" with the International Committee of the Red Cross and met recently with the World Health Organization's director-general. Many of the hostages are in need of "urgent medical care," based on information they have received from those who were released, according to Levine.

"This is purely a humanitarian issue," Levine told ABC News at the forum's headquarters. "The hostages could be saved."

"The clock is ticking. The time to act is now," he added. "It's an open wound for the community as long as not all of them are back."

Back at home, Orit said she can feel her son's presence most when she lays awake at night.

"These are the moments I can talk to him," she told ABC News. "These are the moments that I'm crying, that I'm weak, that I send him lots of strength."

When asked if she had a message for her son that she wanted to share, Orit broke down in tears as her voice cracked and quivered with emotion.

"Almog, be strong," she said. "We do everything we can to bring you back. We love you. We wait for you."

ABC News’ Yitzhak Nakash, Juan Renteria and Magnus Macedo contributed to this report.