Addressing his fans on his online channel that allows Peter to upload videos, messages and news on the site, the Australian singer talked about the "commotion" the speculation had caused.
He cleared the engagement rumours in a video entitled, The truth about Emily and marriage.
"[The reports] forgot to put the word 'yet' in there," said Peter. "Without that word 'yet', it caused a commotion."
"When I do do that, it'll be between me and her. She'll be the first to know. I can promise you that."
Just last week it was speculated that Peter was going to propose to his girlfriend who is thought to be around four months pregnant.
The Mysterious Girl singer was reportedly said to be shopping for engagement rings and even considering buying a rock worth £60,000, causing Peter to address the issue in his video.
Peter met the 23-year-old medical student Emily through her father, a doctor who performed surgery on the singer in 2010.
Speculation that Emily was pregnant started when Peter was seen placing his hand on her stomach at an event in June.
"We were going to keep this to ourselves a little bit longer, but as everyone's been asking, I am very happy to tell you that Emily and I are having a baby, and we are over the moon," Peter shared in his column.
"Emily will make a brilliant mum," he added.
The baby will be Peter's third child – he already has son Junior, eight, and five-year-old daughter Princess with ex-wife Katie Price – and his first with Emily.