Shakira says motherhood is the ''hardest job on earth.''

The 'She Wolf' hitmaker, who has sons Milan, two, and Sasha, nine months, with boyfriend Gerard Pique, admits she questions her ability to be a good parent on a daily basis.

The Colombian singer said: ''I'm one of those tiger moms, who is all the time looking for help and information online and researching and reading. It's not easy to be a mother.

''It's one of the most difficult things I've done in my life. I've been on the most challenging stages performing in front of really demanding audiences and I've been meeting with world leaders who sometimes make you a little bit apprehensive, but nothing has made me so self-conscious as being a mom. Every day I wonder if I'm doing the right thing. I just want to improve in the job, the hardest job on earth.''

But Shakira, who has developed a line of toys and and an app with Fisher Price to help parents educate and nurture their children, believes ''love is the most crucial thing'' she can give her children.

She told PEOPLE.com: ''It's what really will help them thrive later on in life ... That is the question that I ask myself every day when I wake up. 'Am I making my kids feel loved?' This is the daily bread in my life. The everlasting question mark ... because I know that that is going to be the most vital component and sense of security in life.''