Looking healthier and acting more rationally than she has in years, Britney Spears seems well on the road to recovery, but a new book Stalking Britney: Britney Under Siege by author Ian Halperin cautions that the 26-year-old may not be out of the woods yet. “She’s on a high right now, but her life goes in circles,” investigative journalist Ian Halperin says in an interview with In Touch. “It’s like a roller coaster ride. She’s a person who is highly sensitive, and just one little thing could set her off.”

In his explosive upcoming tell-all book, Stalking Britney: Britney Under Siege, the New York Times bestselling author explores the secret pain that he alleges drove Britney to attempt suicide four times following her split from ex-husband Kevin Federline. Halperin researched this sensational book during 18 months undercover as a photographer.

The pressures of her career — which began at 12 as one of the youngest cast members on The New Mickey Mouse Club — led to her deep insecurities. “At 15, she had a huge breakdown and had to return home to Louisiana,” he reveals. “She was very insecure and felt like she wasn’t pretty.” But rather than get help, Britney focused on her outward appearance: “She went on a huge diet.”

Today, Britney is on medication, but Halperin believes she’s far from recovered. “There’s no doubt, based on the last two years, that she is a highly unstable person,” he observes. “She’s on a temporary high right now, but she’s never really dealt with all the problems she had. I don’t think it’s possible to turn over a new leaf just like that.”

Yet as far as Halperin is concerned, Britney deserves to get better — and to lead a happy life. She’s a “good mother, and a good person,” he says. “In fact, she’s nicer than most of the stars I’ve met. But as Britney once told me herself, her life has always been two steps forward, followed by one step back.”

For more check out the new In Touch, on sale now.