The Take That singer appeared on a special episode of the chat show, which was dedicated to the 42-year-old star.
Sitting by his wife Ayda Field in matching outfits, he talked about his history with depression and the difficulty we went through trying to turn his life around.
He said: '[Depression and anxiety] didn't exist when I was battling it - thankfully we're in brand new times now and it's talked about - it's not "poopooed" any more. I felt more and more isolated because I was told to just get on with it.'
Robbie added that as he didn't know what was wrong with him, it led to his drug and alcohol abuse spiralling out of control.
'I didn't know what was going on, I didn't know there was something to talk about, there was something to say.
'You don't know to label it as anxiety, you don't know to label it as depression, and I went on the roller coaster ride of drugs and drink and I masked it. So I was medicating.
'And then the medication and my hedonism was way too much for life and I had to stay on the planet because I quite like it here and I had to do something about it.'
Robbie praised his wife Ayda for helping him change his ways, while she added that they're not going to hide the past from their children.
'We'll be very open with [our children] and we are now. We both come from heavy therapy and we like to be very honest with them about it. And I know it sounds hippy but it's what we believe.'
Speaking about his wife and personal struggles, Robbie added: 'My life is way better because Ayda is in it. My life is richer now because of what I have been through. I still have those downs but right now I'm up here.'
Robbie has also written a song dedicated to his two children, Teddy and Charlie, called 'I Love My Life'. He later teared up, as The Loose Women panellists showed a video of Teddy singing the song to her dad.
Choking back a few tears he said: 'I wrote that song about the kids and she started to sing it by herself and she didn't know that it was about her. She runs around the house singing it with a balloon.'
It's not the first time Robbie has opened up about his personal battles as he recently told the BBC how having a family has made him happy.
He said: 'I'm a daddy, so I have a purpose. It all makes sense. I'm a working dad, whereas before I was the textbook pop star who wasn't happy, even though he's got all this stuff.'