'Sons of Anarchy' star Charlie Hunnam revealed that he dropped out of the movie 'Fifty Shades of Grey' because of his busy schedule.

Before Jamie Dornan was cast as Christian Grey, Charlie Hunnam surprised his fans when he agreed to be the lead male character to the movie adaptation of E.L. James' adult novel 'Fifty Shades of Grey'.

However, two months later, Hunnam backed out of the movie.

In an interview with Us Weekly at a Television Critics' Association party, Hunnam explained his decision to drop the part as an eccentric billionaire.

"I wouldn't have signed up in the first place if I didn't want to do it. It was a really, really difficult time in my life. I had already been attached to 'Crimson Peak' for about 14 months, which I said, I was going to do with Guillermo [del Toro]," Hunnam explaines.

According to Hunnam, he loved the creativity that director Sam Taylor-Johnson applied to 'Fifty Shades of Grey'.

"I fell in love with the character and started seeing him and becoming intoxicated, which is the way I work: I find a character I love and I start thinking about it all the time," Hunnam said.

However, the role of Christian wasn't the only one Hunnam was playing at the time. The 34 year old actor was also busy playing the role of 'Sons of Anarchy' lead Jax Teller, as well as his role in Guillermo del Toro's upcoming film as Dr. Alan McMichael.

"I was going to finish [filming] 'Sons' at like 11 p.m. Friday night, get on the plane Saturday morning to Vancouver for 'Fifty,' missing the whole first week of rehearsal, and start shooting Monday morning," Hunnam explained.

"And I was going to shoot that film, wrap that on the Wednesday and the following Monday I was going to start shooting 'Crimson Peak' in Toronto," Hunnam added.

His schedule proved to be too much for Hunnam, "I just had like ... frankly, something of a nervous breakdown," he said adding, "... I just said, 'I can't ... I can't ....'"

According to Hunnam, he was scared of being the cause of disappointment in the highly-anticipated movie.

"... because 'Fifty's' going to be massive, it's going to be huge, I really didn't want to fail on such a grand scale, and I just couldn't transition from Jax Teller to Christian Grey in 48 hours," the 'Sons of Anarchy' star explained.

Meanwhile, the producers of 'Fifty Shades of Grey' released a new teaser photo in honor of the birthday of the lead female character, Anastasia Steele, played by Dakota Johnson in the film.

'Fifty Shades of Grey' debuts in theaters on Feb. 13, 2015.