After experiencing mild chest discomfort and fatigue on while on tour with his band in Europe last spring, Carter scheduled a series of tests with a Florida cardiologist.
But the night before his results were due back, Carter, 29, fell into a familiar routine: "I went out and just went nuts," Carter tells PEOPLE in its new issue. "I drank so much and I did a bunch of blow. I felt like I was trying to kill myself – because I didn't want to get the results."
See an exclusive PEOPLE video of Carter opening up about his struggles
The years of abusing his body led to a shocking diagnosis: cardiomyopathy, a weakening of the heart muscle that, in extreme cases, can require a transplant or lead to sudden death. (It's the same condition that led to the death of singer Andy Gibb at 30 and killed actor Chris Penn at 40.)
After a few slips early on – and some blunt talk from his cardiologist – Carter sobered up and got healthy. At 167 lbs., he's now in the best shape of his life.
Today, says Carter, life is "awesome."
For more on Carter's recovery – including how his tumultuous family life affected his struggles, why he moved from L.A. to Nashville, and the secret behind his dramatic 57 lb. weight loss – pick up this week's issue of PEOPLE, on newsstands Friday
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