'I'm going to get a sore back' Liam Payne reveals that baby Bear is 'humongous'

Liam Payne has opened up about an unexpected side effect of becoming a dad - back pain!

The One Direction star, who welcomed his first child with partner Cheryl back in March, said that his son had been growing surprisingly quickly, describing him as a 'big boy' and a 'chubster'.

'He's just big in general — he's humongous!' Liam, 23, exclaimed to PEOPLE magazine during an appearance at Musical.ly headquarters.

'I'm going to get a sore back. He's a big boy! He's healthy, he's strong, he likes his bouncer.'

He added that he had been starting to see a a resemblence between himself and the four-month-old.

'I thought he looked like me, but then I saw a picture my mom sent me of myself when I was a baby and I was like, "Whoa",' he admitted. 'I was a chubster baby.'

Cheryl, 34, has kept largely out of the public eye since baby Bear's arrival, only taking to social media on rare occasions, but Liam has been giving fans much more regular insight in to their life as a family of three.

During an interview a Q&A session earlier this year, he shared Cheryl's adorable nickname for the little one, explaining that she calls him Cub.

Liam has also made no secret of the way that fatherhood has altered his day-to-day routine.

'The moment that little boy or girl looks in your eyes your life is changed forever,' he admitted on The Kyle and Jackie O Show back in May.

"When he was first born... I had never even changed a nappy. I never had any younger siblings or people to change nappies on.'

'It's not something I would partake as a hobby... I don't know if I'm speaking on behalf of other dads but you work on your feet because you have to it's your responsibility.'