After a two-year battle with a lack of motivation, 14-time Olympic gold medalist Michael Phelps is aiming for a strong comeback at the FINA World Championships and still has his eyes set on breaking world records.

After grabbing a history-making eight gold medals in a single Olympic Games in Beijing, the American superstar swimmer went missing over the past two years; consistently losing events and even getting involved in a marijuana scandal.

However, having "recharged himself through a bumpy journey", Phelps claims to be back on the right track and refocused on next year's London Games.

"I realized I had to take responsibility for the things I do in or out of the pool I was hurting myself. That's what I learnt after a low time the last two years," Phelps told a packed press conference on Saturday.

"If I want to accomplish my goals, I have to take charge of myself. I have to do it myself although (coach) Bob (Bowman) has pushed me every day. I can't be lazy any more and actually should do something.

"It's been a good experience over the past six months (to go through the highs and lows). It's a learning process. Hopefully, I can use it as a motivation for London," said Phelps, who will only swim four individual events in Shanghai.

Although he departed the 2009 Rome worlds with five gold medals and broke the 50-second barrier in the 100m butterfly, Phelps surrendered the 200m freestyle world title and record to Germany's Paul Biedermann and has since also lost to China's top swimmer, Wu Peng, in 200m fly twice this year.

However, Phelps shrugged off those defeats, stressing he has learnt from "those races on how to fix things the next year".

"I am in a lot better shape than last year. I have more confidence. I didn't work things as expected last year. This meet is a kind of test for my body (to see) if it can handle things for next year," said the 26-year-old.

Bowman, who discovered the restless youngster's Olympic gold potential in 1996, hailed his student's awakening as a "pleasantly surprise" and it attributed to their deep bond.

"We are very truthful to each other no matter which kind of situation we are in. We have open communication any time," said Bowman, who encouraged Phelps to try a new freestyle stroke to help him meet the demands of the 100m event.

But he said a decision on Phelps competing in the 100m in London would not be made for a while.

"We don't know that yet. The challenge this year is doing an entire training cycle in a more compressed way, as we will do a year-long plan in nine months. How it works, we are going to find out shortly here," said Bowman.

Coming back to the nation where he reached his career peak, Phelps said he felt excited about recalling the great memories and looked forward to breaking more records.

"I know a lot of the world records are super fast now and will take a lot to break. But I still see the records are reachable and can be broken this week," Phelps said.

He also also admitted it would be tough for him to quit the pool, from which he is expected to depart after his third Olympic appearance next year.

"It will be really weird to hang up my shoes and to say goodbye to all the memories I went through. It's hard for me to think about it," he said.