Lindsey Roberson remembers thinking: "If you've ever given something every bit of your strength, this is it"

As a girl, Lindsey Roberson went to Camp Mystic, on the banks of Guadalupe River in Texas — and this summer, she was happy that both her daughters were campers there, too.

“It’s our safe, happy place,” says Roberson, a 47-year-old real estate agent. “Mystic was our heaven on Earth.”

Her daughters, 17-year-old Riley and 13-year-old Molly, were on senior hill at Camp Mystic on the Fourth of July as deadly floodwaters started to rise.

The girls were successfully evacuated, but it was Roberson, her 15-year-old son, Jack, and her husband, Phillip, who had to survive their own ordeal back home in Ingram about seven miles away. They lost their dream home and plan to rebuild.

Here, Roberson shares her story of narrow escape from the rushing river: "I do not know what happened for me to survive. My kids are embarrassed that I'm telling people I'm a miracle.”

'This is a nightmare'

My two dogs were barking at 3:30 in the morning because they were scared of the storm. I took them outside and it was raining. I went back to sleep. My husband woke me up at 5 in the morning and said, "Our house is flooding." The water inside was a foot high — outside, the water was higher than the windows.

He was like, "This is a nightmare. Go wake up Jack."

My son is 15, and he did not want to wake up. I was like, "You have to get up or we are going to die.”

Jack and I went downstairs and we couldn’t find my husband. It was pitch black. We were screaming for him. We're calling his cell phone. He was not answering.

Jack was like, "We have to get Daddy."

I said, "We have to go because I have to keep you alive. We're out of time. He's the smartest person I know and he will be safe.”

Meanwhile, my husband was trapped in the bathroom where the water is rising. He finally busted the door open, water came rushing in, he swam to the stairs and was able to climb to an upstairs bathroom and break the window and climb onto the roof.

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.

My car washed away. We got into my husband’s truck and started driving — I thought we could make it out, but the truck started floating. We called 911 and they said to go out the truck window.

We got out and the water immediately took us away. We were still together, then Jack said, "I think our fence just hit me in the back, Mama, I can't feel anything."

He washed away from me in the black water in the dark, and I was screaming, "Jack, Jack!" I thought I lost him.

'I got a tree and held on'

The current was so strong — I grabbed onto a tree. There were boats coming at me. Our fishing boat came at me, and I climbed in. But I knew that I couldn't control it, so I let the boat go.

I heard Jack screaming, "I'm in a tree."

Then I saw a house coming at me. I went underwater. I feel like God held me down until the house passed. I thought, "This is it. This is how I'm going to die." Then I remember thinking, "No, I can't die. I'm a mom. I can’t die. I can do this.”

I fought to get back to the surface and grabbed onto a two-by-four and floated down the river.

Jack was still screaming for me. He had his phone’s flashlight on, so I was trying to swim to the light, but the current was so strong I couldn't. I got to a tree and held on.

Everything that was coming down the river was so scary. My leg was hurt and my foot was hurt, but I was like, "Lindsey, if you've ever given something every bit of your strength, this is it." I climbed as high as I could up that tree.

I was screaming to Jack, "We need a boat. We need to be rescued. We need help."

I kept screaming for help — my mouth would get dry, then it would start raining and I’d stick out my tongue and try to get some rainwater so I could scream again.

Jack made a video for 18 minutes straight: He took the video so neighbors would know where to find us.

He was calling 911 and he was sending our location and I was screaming, "You need to send an SOS."

The water started receding when it started getting light outside. There were no branches or anything. I was 15-20 feet high. A friend helped me get out. My leg was cut; my husband says it looks like a shark bite. A friend loaned my husband a truck so he could drive me to the hospital.

Meanwhile, my daughters were being evacuated from Camp Mystic. I had to go get them. I couldn't wait to see them. They were safe and we were all reunited. That was amazing.

We had people show up immediately. My friends have shown up like you would not believe — strangers, volunteers.

Two days later, the cut on my leg got infected. I had to go to a hospital in San Antonio and have surgery.

We just have to go day by day, and God will give us what we need. But if we start looking too far past today, we get overwhelmed and we can't handle it. And so we just have to really focus on what are we doing today, and we're worrying about tomorrow — tomorrow.

Life is precious, and we need to live every day. Don't take anything for granted. Spend time with your family and your loved ones because you just never know what's going to happen tomorrow.

God is good. We have to stay grateful, hopeful and positive.

This interview has been edited and condensed for clarity.