Kylie Jenner is "very self-conscious" about her body changing throughout her pregnancy

A source said: "Her body is changing and she's very self-conscious about it. She's always been insecure that she's not as curvy or pretty as her sisters."

Kylie and Travis are said to be trying to keep the news private for as long as possible to avoid a media frenzy, and while they are keeping things under wraps, the 25-year-old rapper is "so excited" about becoming a father.

The source added: "Travis is so excited about the baby. They're both trying to enjoy this time for themselves and keep it private as long as they can. They know it's going to be a frenzy when they do come out.

"Travis is crazy about Kylie and he feels so lucky to have her and the baby.

"The family has been welcoming - they know how important it is to Kylie that everyone gets along."

While Kylie's pregnancy is yet to be confirmed, the 'Keeping Up With the Kardashians' star is said to be "having fun" teasing people about the news.

A source close to the star told PEOPLE: "Kylie is only trusting her closest friends and her sisters right now. She wants to reveal things on her own terms but she's of course having fun teasing everyone.

"She knows all the attention is on her and her baby bump, but she won't share until she wants to."