"Ever since I was born, I've been living under the mistaken belief that I was brain damaged,” says the 52-year-old Scot, who found worldwide success after being discovered on hit show Britain's Got Talent.
"Doctors told my parents that I was starved of oxygen at birth and that this had caused me brain damage, leaving me with learning difficulties and a lower than average IQ.
"At school I was pushed aside as if I didn't matter, while the brighter pupils got all the attention. I was mocked and bullied.
"As a result, I spent my whole life in a bubble, felt inferior to others and had problems forming proper relationships.
"Now that I know the correct reason why, I understand myself better and can move on. It feels as if an enormous weight has been lifted."
A form of autism, Asperger's sufferers typically struggle with their emotions, find it difficult to understand non-verbal social cues and feel anxious in social situations.
It has been Susan's crippling anxiety that has prevented her from embarking on a tour since she shot to overnight fame four years ago. This week a special ITV documentary There's Something About Susan follows her as she attempts to fulfil her ambition to perform a live concert for the first time.
"The message that I hope my revelation will give others is, if I can do it, so can you. No matter what your condition, you can do whatever you want."
See the full interview with Susan in HELLO! magazine, out now.