The German World Cup winner, who joined Arsenal in 2011, is retiring at the end of the season ahead of a new role with the Gunners' academy from next season.
In an interview with Spiegel, Mertesacker said that he will be glad to retire from football after a long battle with the illness.
"My stomach starts churning and I feel like I'm going to throw up," the 33-year-old said of his experiences. "Then I have to choke so hard that I tear up. I have to go to the bathroom right after getting up, right after breakfast, again after lunch and again at the stadium. Everything that then happened, symbolically speaking, just made me want to puke.
"You don't want the other people on the team to think there's something wrong with you. That competitive sports maybe isn't right for you.You joke around in the dressing room, have closer contact with maybe two, three people. But that's it. Nobody lets down their guard and says how they really feel.
"Everyone says I should really savour the last year, play as much as possible, really soak everything in," he said. "[But] I'd most like to sit on the bench, or, even better, in the stands. I will, at an age of over 30, finally be free for the first time in my life."
Arsenal's last result saw them move into the last eight of the Europa League with victory over AC Milan in North London.