Robbie Williams made his baby daughter sick with a song he wrote for her.The proud pop star dad has penned the track 'Go Gentle' for five-month-old Teddy - his first child with wife Ayda Field - but when he sang it to the tot she vomited.He said: "Teddy got her first song. It's called 'Go Gentle'. But it might be called something else by the time it comes out. I sang it to her as we walked around the estate. She was in a papoose so she was a captive audience. I think she liked it, then she threw up. Tough room."Robbie has also revealed he has been on a major fitness regime and diet and has lost 24lbs in five weeks.The 'Candy' singer turns 39 tomorrow (13.02.13) and as he rapidly approaches his 40th birthday he realises he has to be far more careful about what he eats.Writing in a blog post, he said: "I went on a diet - knocked out sugar (processed) and dairy. Lost 24lbs."Seeing as 40 is just around the corner it's time to go all yoga and lentils. Who knows where it could all end."Robbie also revealed he is working on a big project and is collaborating once again with songwriter Guy Chambers - who is responsible for penning some of his biggest hits including 'Angels', 'Rock DJ' and 'Let Me Entertain You'.The star revealed: "I've been working on another 'big project' ... not just sat on my arse being a daddy. Although I've done my fair share of that too. All will be revealed, needless to say I'm excited about what's to come."Me and Guy worked together for the first time in many years. Funnily enough we're a good team. What a treat. I luvs him (sic)"