Poynter found himself struggling without the since-reformed McFly despite being the one who suggested they come to an end in 2016.
The musician, who attempted suicide in 2011, relapsed after falling out with his bandmates and friends Tom Fletcher, Danny Jones and Harry Judd.
Speaking in new documentary McFly: It's All About Us, Poynter said: “On the one hand, I felt inspired because friends in LA would take me to see other bands and stuff.
“On the other hand, I was like, ‘But my band’s broken and it’s all my fault’.”
Poynter said that “Valium was a way of just making all that disappear”.
Fletcher, Jones and Judd soon realised that Poynter was “taking something”, with Judd saying: “He sort of told me what he’d been taking – he was like, at that lethal dosage”.
In an attempt to repair their friendship, Poynter asked his bandmates to join him at group therapy.
Judd acknowledged that, while there may have been hard feelings initially, “we realised Dougie did nothing wrong – and that’s the biggest lesson from all this”.
Speaking about being a part of McFly, Poynter, who won I'm a Celebrity in 2011, said: “It’s all I really know and all I really want to know.”
McFly: It's All About Us airs on Saturday 14 November at 6.40pm on ITV
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