Joe Jonas has opened up about his past relationships, including his short romance with Demi Lovato, confessing he only stayed with the singer to help her deal with her drug abuse problems. The Jonas Brothers heartthrob began dating his Camp Rock co-star in 2010, but their relationship was extremely short lived, lasting only four weeks. In a candid interview with New York Magazine, Jonas reveals that dating Lovato was way more than he anticipated, especially because of her ongoing struggle with drug addiction. He admits, "One relationship that meant a lot to fans was the one I had with Demi Lovato, who I've known for years. We had been friends forever, we were both Disney kids - we eventually dated for a month. "I really got to know her and got to see the ins and outs of what she was struggling with, like drug abuse. I felt like I needed to take care of her, but at the same time I was living a lie, because I wasn't happy but felt like I had to stay in it for her, because she needed help. I couldn't express any of that, of course, because I had a brand to protect." He continues, "It was an insane situation to be in. Things kept building up, and Demi ended up punching a girl in the face on a plane, because she thought the girl was blaming her for something. Everybody gasped, and the girl just started bleeding. "That's when her team and her family told her, 'You need to go into rehab.' I remember being in South America, and fans immediately jumped to the conclusion that we kicked her off the 2010 tour, and they just hated on us for it." Lovato subsequently went to rehab for her drug addiction and depression issues, and has been sober ever since. Jonas also reflects on the demise of another relationship with Twilight actress Ashley Greene, whom he dated for a year until 2011. He says, "I was living out in L.A. by myself, and at the end of the day, long distance didn't work. It's incredibly difficult. I did a cover story with Details (magazine) acknowledging the relationship, and the day after it was on newsstands, we announced our breakup. That was just coincidence, but it's funny how that always happens, right? "After Ashley, I took two or three years to just be single. I was hooking up and having fun. Now I'm with someone I really care about. We get each other." Jonas, who has been dating model Blanda Eggenschwiler since last year (13), also confessed he's romanced fans in between his celebrity relationships, including ex-girlfriends Camilla Belle and Taylor Swift."