Leonardo DiCaprio believes his career is the reason he has been unlucky in love.The 38-year-old actor - who has dated a string of top models including Gisele Bundchen, Bar Refaeli and Erin Heatherton - admits shooting movies all over the world has made it difficult for him to hold down a relationship.The 'Great Gatsby' star told the May issue of Esquire magazine: "Six months of being on location or being off in Morocco or someplace like that is not the best thing for a relationship."Leonardo, who has most recently been linked to former Miss Universe Kosovo Aferdita Dreshaj and his 'Wolf of Wall Street' co-star Margot Robbie, also revealed that he always felt like an "underdog" in Hollywood despite being nominated for three Oscars and struggled to cope with fame until recently.He said: "I didn't have nice enough clothes or maybe my hair didn't look good. And so you have to understand - getting your foot in the door is like winning the lottery. It's literally like winning the lottery if you get to have a career."And I've always felt, Okay, now I've gotten this shot, and I'm lucky to have gotten this shot, and if I don't do this to the best of my ability - if I don't work my a** off and make a life of it - I've squandered this incredibly golden opportunity. And that's always been, what has propelled me."I really didn't understand what fame was and I didn't understand what being in a giant hit was and I didn't understand what a giant hit 'Titanic' was compared to other giant hits."There was no rule book. There was nobody to navigate me through the experience of being watched all the time and nobody to tell me how to be normal when everybody is acting and looking at me differently."But he now feels more comfortable in the spotlight and is currently enjoying a career break.He said: "Most recently, in the last few years, I feel way more comfortable than I've ever felt."