An explosive tabloid report this morning claims that Britney Spears was assaulted by her boyfriend Jason Trawick, and that she was pregnant at the time.

He also cheated on the pop star with a teenager, supposedly.

A main source cited in this Star Magazine cover story is Jason Alexander, Brit's former husband (albeit for less than three days) way back in the day ...

STARTLING ALLEGATION: Was Britney Spears attacked by Jason Trawick?

Doctored or not, the cover does show a photo of Britney’s black eye, which Jason Trawick allegedly provided after she accused him of straying.

Perhaps most shockingly, on top of the beatdown, the magazine claims Britney Spears was pregnant with his baby at the time ... and no longer is?

While it's impossible to believe much that Star says, this is unusually inflammatory, borderline libelous stuff to concoct and run for no reason.

What do you think? Could there be any truth to this whatsoever? Spears' official site hasn't denied it on its "BS Alert" ... yet. Stay tuned.