United Kingdom, Aug. 28 -- Britney Spears "felt like a robot" during her pop career.

The Toxic singer has looked back on her former life in the music industry and confessed she's "changed big time" in the last few years with Britney confessing she suffered from panic attacks during meet-and-greet events with fans and she "can't believe" she used to be able to "perform in front of so many people".

In a post on her Instagram page, Britney wrote: "Let's just say I've actually changed big time. I honestly can't believe I used to be able to perform in front of so many people.

"Good lord. I'm so sensitive and proud of myself for shutting all that down, 'cause for too many years it was forced.

"When I used to work with [longtime assistant] F...