The 25-year-old singer - whose first child with boyfriend Sam Cooper is due in February - confided in pals after having an ultrasound scan to discover the gender of the tot.
A friend told The Sun newspaper: "Lily said she found out from a scan she is having a boy.
"She is really excited and can`t wait to give birth. She is always asking other mums about their pregnancies."
The `Fear` hitmaker - who is said to be looking into antenatal classes and yoga to help her through the next five months - is enjoying pregnancy but is struggling to contain her feelings of sickness and can`t stop drinking soup.
She told the Daily Mirror newspaper: "I could do with a great big cup of soup right now. Chicken, tomato - whatever I can get. That`s all I`ve really been craving.
"I could have it for breakfast, lunch and dinner. I`m serious - I just can`t get enough of it.
"The past few months have been a bit tough because I`ve been sick and stuff, but now everything`s fine, because I`ve discovered soups are the cure to my morning sickness."
Lily - who suffered a miscarriage in January 2008 - recently admitted she spent much of her first three months of pregnancy terrified something would go wrong.
She said: "I had about a week and a half of really heavy bleeding and had to have lots of scans, that`s when I had to cancel my gig in Spain. I`ve been living in fear for the past three months."