Aaron Carter broke down in tears while defending himself after being arrested for driving under the influence and drug possession.

The 29-year-old singer told Entertainment Tonight on Tuesday that a motorcyclist reported seeing him "swerving all over the road," which he blamed on his car being out of alignment. TMZ audio from a 911 call says Carter drove past a parked cop while drifting from the median to a guardrail.

Carter insists police never witnessed him driving "erratically," and says he can't be charged with DUI because they approached him while he was inside an AutoZone in Georgia.

"[They] forcefully grabbed me out," he claims. "[I] stepped outside. I say, 'I invoke the right to speak to my attorney,' and they disregarded that, they revoked that immediately. They said, 'Is there anything illegal in the car?' I said, 'I have marijuana in the car.'"

Carter, the younger brother of Backstreet Boys singer Nick Carter, said he last smoked medical marijuana nine hours earlier to treat anxiety, chronic pain and help with his appetite. Carter added that he was driving because he hasn't been comfortable flying since witnessing the terrorist attacks in New York on 9/11.

"I opened for Michael Jackson Sept. 9 and 10 in 2001 -- we all left the morning of Sept. 11 and watched the Trade Centers get hit across the Hudson River, and I saw it with my own eyes and I saw people jumping out of the buildings and burned," Carter told ET.

The pop star, best known for 2000 hits "Aaron's Party (Come and Get It)," "I Want Candy" and "That's How I Beat Shaq," cried as he expressed concerns about his girlfriend Madison Parker, who was arrested for obstruction. He added that he felt like many people "gave up on me," including Nick.

"To my brother: I love u no matter what & if u feel the need to reach for help, I am here and willing to help you get better," the Backstreet Boys singer wrote on Twitter.

Aaron Carter also said he doesn't drink alcohol due to medication he's on, including "Xanax, Propranolol for high blood pressure medication, and... oxycodones for my (jaw injury)." He's cited health issues including an eating disorder and a hiatal hernia, which caused him to lose weight uncontrollably in recent months.

Carter admitted trying ecstasy "a couple of times" when he was 16, but denies ever taking crack cocaine, meth or taken heroin.

Last month, he checked himself into a Syracuse hospital after fans allegedly "bullied" and "body-shamed" him at a HOT 107.9 concert in Liverpool. He hinted at struggles with exhaustion after a rough month: His father Bob Carter, former owner of the Yankee Rebel bar near Buffalo, where Nick was born, died at the end of May; and June would've been the 31st birthday for Nick and Aaron's sister Leslie Carter, who was found dead of an apparent overdose in Upstate New York in 2012.

He's threatened to sue the Habersham County Sheriff's Office over his arrest, claiming he was targeted by cops because of his "celebrity."

A rep for Carter told People magazine that he has "nothing against the police" and understands they were doing their job, but was protective of Parker, who had never been arrested before. Carter added that he doesn't need rehab and denied being addicted to drugs.

"I don't need help," he told the publication. "What I need is for people to understand that I'm human and that I make mistakes just like every other human in this world, but I would never risk my life or my girlfriend's life."