Justin Timberlake has ''become a mess'' since he became a father.

The 39-year-old singer-and-actor admitted he is much more emotional these days and watching five-year-old Silas - who he has with wife Jessica Biel - learn and develop often reduces him to tears.

Asked what makes him cry, he said: ''I'm a softie, man. Watching your son learn the smallest thing can bring you to that place, for sure. I have become a mess since I became a father.''

The 'Trolls World Tour' star sometimes struggles to express himself but finds it easier to find his voice in his songwriting, and the happier he feels, the easier it is to open up.

He said: ''There are times, especially pre-coffee in the morning, where it's hard to express yourself.

''But through songwriting, I can sometimes express the complexity of an emotion that I couldn't otherwise.

''For me, the more I enjoy being an artist, a dad and a husband, I find the more I'm able to express that.''

Justin is thankful he can be ''picky'' about the projects he can take on and he's always looking for something ''really inspiring'' that will justify him working away from his wife and son.

He added to OK! magazine: ''I always want to continue to be inspired.

''At this point in my life, I can be picky about the projects I'm going to work on.

''I choose wisely because I know it takes a lot of time to do the type of work that I want to do, whether it's making music or a film - or both in the case of 'Trolls World Tour'.

''That time takes you away from your family, so it had better be something really, really inspiring.''