The Italian's positive test was revealed two days ago when the 27-year-old, who now believes his career is over, was provisionally banned by his national Olympic Committee.
"When you wait for your girlfriend to go to train so that you can lock yourself in the bathroom and inject EPO in your veins so that no one will know, it's not nice," Schwazer, weeping openly, said in an hour-long news conference.
By injecting Erythropoietin - better known as EPO - athletes aim to increase the concentration of red blood cells and consequently their aerobic capacity and athletic performance.
Flanked by his lawyer and his manager, and with his father in the audience, Schwazer referred to his girlfriend - world champion figure skater Carolina Kostner - repeatedly, saying he regretted lying to her.
Schwazer suggested he actually wanted to get caught because the guilt was psychologically devastating. He said he could have tried to skip the July 30 doping test knowing he had made a final injection a day earlier, but did not.
"I'm not made to take drugs or to deceive people, and I couldn't take it anymore. I couldn't wait for the whole thing to end," he said.
"When on the 30th (of July) the doorbell rang I knew it was the anti-doping people, I knew it was all over. It would have been enough to tell my mum not to open the door or to tell them I wasn't home. But I couldn't take it anymore."
Even if he had not tested positive, he said he would not have gone to London for the 50 km race, which is scheduled for Saturday.
Schwazer now hopes to lead "a normal life" away from athletics where he sees his girlfriend every night "instead of just twice a month".
"Carolina loves her sport. She skates because she likes it. I race walk because I'm good at it, but I don't like doing the same exact thing 35 hours a week, and sometimes at night when I'm shattered and thinking about getting up the next morning and doing it again," he said.
"The race walk was making me nauseous. I couldn't stand the training anymore."
The athlete said he had continued to race walk despite wanting to give up because of external pressure and that he probably decided to take EPO because he was worried about being able to perform in both the 20km race and the 50km race in London.
"I made a huge error," he said. "And I can only repeat, I'm sorry.
"(There were so many) expectations that I had to dominate even more than before.I couldn't say no to this decision to do doping for the 2012 Olympics."
Schwazer, who set an Italian record in the 20km in March, had been one of Italy's big medal hopes in a sport where athletes move as fast as they can while keeping one foot in contact with the ground at all times.
He raised eyebrows when last month he suddenly pulled out of the 20km race, saying he had had a bout of flu.
Schwazer, who became a hero in Italy four years ago after he won gold in Beijing by knocking more than a minute off a 20-year-old Olympic record, told his doping tale in great, and sometimes disturbing, detail.
His story clashed starkly with the athlete's clean-cut image that is highlighted in a ubiquitous Italian advertisement for Kinder chocolate bars set in the idyllic Alps where he lives.
After studying how to take and buy the drug on the Internet, he said he flew to Turkey in September 2011 for three days, exchanged 1,500 euros for Turkish lira, went to a pharmacy and bought EPO over the counter.
He kept the drug in his refrigerator and told Kostner that they were vitamins, he said.
"It wasn't easy for me to tell her that it was EPO in the refrigerator and not vitamins," he said, adding that she was the first person he called after he was told he was excluded from the London Olympics.
He said he took the EPO only in the month leading up to the Games, that he had acted alone, and denied that he had taken performance enhancing drugs before the Beijing Games.
He challenged the Olympic authorities to re-examine his blood from four years ago.
Ansa news agency reported that Bolzano prosecutor Guido Rispoli had opened a probe against Schwazer into whether he committed the criminal offence of sporting fraud, which carries up to a three-year jail sentence.
He also faces disciplinary action by a military tribunal because he is a member of the military police, or Carabinieri, Ansa said.
"What is most important for me is to liberate myself of this weight I have inside," Schwazer said. "I dream of another life."