The singer-songwriter, who stars with his family on Stewarts & Hamiltons, a new reality series on E!, tells PEOPLE of his drug and alcohol addictions: "I had some really hard times. But my dad never gave up on me no matter what."
Hamilton, 40, began acting in the '90s, but his personal life became tabloid fodder after two quick – and very public – marriages. (His five-month union to Shannen Doherty ended in 1994; he split from Angie Everhart in 1997 after three months.)
"It overshadowed my work," says Hamilton of the attention. "I went underground, a little short sabbatical."
And Hamilton had already been dealing with painful problems. He admitted to PEOPLE in 2013 that he had suffered from eating disorders beginning as a teen; he also struggled with addiction.
Now, Hamilton, who is sober and has a new album, says he's happier than ever: "My dad always said, 'You'll get a second chance.' And now I have one."
Stewarts & Hamiltons premieres Sunday at 9 p.m. ET on E!.
For more on the Stewarts and Hamiltons, pick up the latest issue of PEOPLE, on newsstands Friday