Pietersen is feeling homesick
Kevin Pietersen has admitted losing the England captaincy and the team's lack of success on the tour of the West Indies has taken a toll on him.
Pietersen, 28, quit as England captain in January after a rift with coach Peter Moores, who was sacked.
"What happened drained me mentally and I know people have been watching me and talking about me throughout this tour," he told the Daily Mail.
"It's been a heck of a tough time and I'm at the end of my tether now."
He added: "Really and truly I can't wait to get home."
England lost the Test series against the West Indies 1-0, were beaten in their Twenty20 match and are 2-1 down in the five-match one-day international series after an emphatic eight-wicket defeat in Barbados on Friday, the day after Pietersen's interview came out.
But Andrew Strauss, who replaced Pietersen as captain, said he could understand his predecessor's frustration.
"I think the full context of what he said there was that he was at the end of his tether with us not performing well enough," said Strauss.
"I don't think anyone likes to go through a period when you're not winning cricket matches so I can understand his frustration there.
"Whether it's best for it to come out in the media or not is another thing, but the reality is he has a lot of pride in his performance in playing for England and he's frustrated by that - he and the rest of us need to use that frustration as a means of motivating ourselves to play better."
England's only win so far was a result of West Indies coach John Dyson misreading the total his team needed to score under the Duckworth-Lewis method before going off for bad light.
"It's been a tough tour for everyone because of the simple fact that we've won only one game to date and that was only because of a mistake by the West Indies coach," continued Pietersen.
Being England captain means you have to be a politician and that's something I'm not
"To go through a winter like this is soul-destroying. We all want to play in a winning team and to be beaten day-in day-out, especially after the way we finished last summer against South Africa, is just not good enough."
England's leading batsman, who led England to a 5-0 one-day series win over South Africa last summer, says Strauss is a "top man" but does not give him advice as it's "...been a bit too close to the bone in terms of what happened in January".
Pietersen insisted he does not have any regrets over the way he conducted himself over his resignation but appears unhappy with the role the England and Wales Cricket Board played.
The World Twenty20 takes place in England this summer and Pietersen has been mooted as a possible captain for the national team in that form of the game.
But, despite the fact he will skipper Bangalore Royal Challengers in the Indian Premier League, he said: "I just think it's too soon after what happened between me and the ECB for me to take over the captaincy again if I was offered it for the World Twenty20.
"It's not somewhere I want to go and dive into. After the way I was let down I just don't think I want to get involved in that again."
In terms of the long term, he added: "Being England captain means you have to be a politician and that's something I'm not."