Heath Ledger & Michelle Williams to breakup?

There could be trouble between Aussie star Heath Ledger and his fiancée Michelle Williams reports NW Magazine.

Heath has reportedly postponed his wedding to Michelle indefinitely, sparking rumors the pair are experiencing serious problems.

Heath is said to have become so moody and depressed that Michelle is urging him to stop filming so they can concentrate on trying to save their floundering relationship.

"Michelle thinks Heath's just under too much pressure and taking the role too much to heart," says a source. "She's been trying to urge him to take a few months off from filming, but he refuses."

The couple met in 2005 while working on Brokeback Mountain and became engaged soon after. In October that year they had daughter Matilda, and were considered to be one of the happiest couples in Hollywood.

"Things between them are the worst they've ever been," reveals an insider.