Levi Johnston shows Tyra Banks his "Bristol" tattoo on his ring finger
Karl Giant/Warner Bros.
04/03/2009 AT 12:00 PM EDT
Bristol Palin's former fiancé and father to her child Tripp is talking about their sex life on national television.
Levi Johnston not only says he practiced safe sex "most of the time" when they were together, he also reveals to Tyra Banks
that he believes Alaska Gov. Sarah Palin knew he and Bristol were having sex when they lived under her roof. "I'm pretty sure she probably knew. Moms are pretty smart," Johnston, 18, says in an interview set to air April 6.
The couple, who were high school sweethearts, planned to wed after graduating – but ended up splitting
earlier this year. At the time, Johnston told Good Morning America
that he needed to mature
before getting married.
Meanwhile, now that they are just friends and not romantically involved, PEOPLE has confirmed with a source that Bristol is not dating but has been "texting and chatting" with a high school boyfriend she had before Johnston.
Johnston's mom, Sherry, and sister Mercede, join him on The Tyra Banks Show
, talking about the gag order imposed on them during Palin's vice presidential campaign. "We were supposed to say that all questions need be brought up to the McCain campaign. Other than that we had to say 'no comment,' " explains Mercede.