In the interview, Mr. Musk added that he did not regret his Twitter post — "Why would I?" — and said he had no plans to stop using the social media platform. Some board members, however, have recently told Mr. Musk that he should lay off Twitter and focus on making cars and launching rockets, according to people familiar with the matter.
The S.E.C. investigation appears to be intensifying rapidly. Just days after the agency's request for information, Tesla's board and Mr. Musk received S.E.C. subpoenas, according to a person familiar with the matter. Board members and Mr. Musk are preparing to meet with S.E.C. officials as soon as next week, the person said.
In the interview on Thursday, Mr. Musk alternated between laughter and tears.
He said he had been working up to 120 hours a week recently — echoing the reason he cited in a recent public apology to an analyst whom he had berated. In the interview, Mr. Musk said he had not taken time off of more than a week since 2001, when he was bedridden with malaria.
"There were times when I didn't leave the factory for three or four days — days when I didn't go outside," he said. "This has really come at the expense of seeing my kids. And seeing friends."
Mr. Musk stopped talking, seemingly overcome by emotion.
He turned 47 on June 28, and he said he spent the full 24 hours of his birthday at work. "All night — no friends, nothing," he said, struggling to get the words out.
Two days later, he was scheduled to be the best man at the wedding of his brother, Kimbal, in Catalonia. Mr. Musk said he flew directly there from the factory, arriving just two hours before the ceremony. Immediately afterward, he got back on the plane and returned straight to Tesla headquarters, where work on the mass-market Model 3 has been all consuming.
Mr. Musk paused again.
"I thought the worst of it was over — I thought it was," he said. "The worst is over from a Tesla operational standpoint." He continued: "But from a personal pain standpoint, the worst is yet to come."
He blamed short-sellers — investors who bet that Tesla's shares will lose value — for much of his stress. He said he was bracing for "at least a few months of extreme torture from the short-sellers, who are desperately pushing a narrative that will possibly result in Tesla's destruction."
Referring to the short-sellers, he added: "They're not dumb guys, but they're not supersmart. They're O.K. They're smartish."
Mr. Musk's tweets on Aug. 7 were the most recent of several flare-ups that had drawn scrutiny. He wrangled with short-sellers and belittled analysts for asking "boring, bonehead" questions. And after sending a team of engineers from one of his companies to help rescue members of a stranded soccer team, he lashed out at a cave diver who was dismissive of the gesture, deriding him on Twitter as a "pedo guy," or pedophile.
To help sleep when he is not working, Mr. Musk said he sometimes takes Ambien. "It is often a choice of no sleep or Ambien," he said.
But this has worried some board members, who have noted that sometimes the drug does not put Mr. Musk to sleep but instead contributes to late-night Twitter sessions, according to a person familiar with the board's thinking. Some board members are also aware that Mr. Musk has on occasion used recreational drugs, according to people familiar with the matter.
Tesla executives have been trying for years to recruit a chief operating officer or other No. 2 executive to assume some of Mr. Musk's day-to-day responsibilities, according to people familiar with the matter. A couple of years ago, Mr. Musk said, the company approached Sheryl Sandberg, who is Facebook's second-highest executive, about the job.
Mr. Musk said that "to the best of my knowledge," there is "no active search right now." But people familiar with the matter said a search is underway, and one person said it had intensified in the wake of Mr. Musk's tweets.
In response to questions for this article, Tesla provided a statement that it attributed to its board, excluding Elon Musk. "There have been many false and irresponsible rumors in the press about the discussions of the Tesla board," the statement said. "We would like to make clear that Elon's commitment and dedication to Tesla is obvious. Over the past 15 years, Elon's leadership of the Tesla team has caused Tesla to grow from a small start-up to having hundreds of thousands of cars on the road that customers love, employing tens of thousands of people around the world, and creating significant shareholder value in the process."
Mr. Musk said he had no plans to relinquish his dual roles as chairman and chief executive.
But, he added, "if you have anyone who can do a better job, please let me know. They can have the job. Is there someone who can do the job better? They can have the reins right now."
—Andrew Ross Sorkin contributed reporting.