The Muse singer revealed that he was not prepared for how gory childbirth was when he was presented with his son Bingham just after fiancée Kate Hudson had given birth to him.
In an interview with German Gala magazine, Bellamy said: "I don't understand why no-one had warned me about how horrible it would be.
"The baby's head was weirdly elongated when it came out. That freaked me out a bit."
The singer admitted that when they first took their son home he was petrified about his new parenting responsibilities, but said that he quickly learnt what to do.
Bellamy added: "I had to learn how to change nappies. It took a while before I got used to it.
"First I was petrified - I couldn't believe what was happening. You're in this kind of bubble where everything feels really far away.
"Then you just concentrate on the easy stuff - which I'm not very good at to be honest. But somehow nature makes sure you grow into your role as a father."
The 34-year-old confessed that nothing has made him happier in life than becoming a father.
He added: "I met Kate and fell in love with her. But the best thing that has happened to me since was becoming a father.
"Being a father changes so much - the way you look at the world and yourself.
"There's nothing that's as much fun as a baby - it's endless joy. I'm really happy with everything."
Watch the video for Muse's 'Madness' below: