The 25-year-old singer, who got engaged to Keegan in 2011, said that the duo had ended their relationship three months before it was known to anyone, reported Contactmusic.
"I had a real problem with drinking too much and that was, without doubt, the downfall of our relationship. It made me a different person, even if I didn't think it at the time," George said.
"I can't even remember some of the two years I was with her because I was getting drunk every night," he added.