Heidi Klum -- I Never Cheated on Seal with My Bodyguard

Seal’s accusation that Heidi Klum cheated on him during their marriage is absolutely false ... at least that’s what Heidi is telling close friends.

TMZ posted a video this morning in which Seal said straight out said Heidi was screwing the bodyguard while they were together --- and that is why their marriage fell apart.

Heidi told one close friend today her relationship with the bodyguard was "strictly professional" while she was with Seal.

The friends tell us that since the split, Heidi says she has gotten "very close" to the bodyguard ... who has helped her through the difficulties of ending a marriage

As for the nature of their relationship now ... all the friend would say is it's "undefined." So that's what the kids are calling it these days.