Britney Spears got into a huge fight with her boyfriend Wednesday night, and she ended up out of control, crying, possibly cut, and almost driven away in an ambulance ... TMZ has learned.

Britney got to the Chateau Marmont late Wednesday night with boyfriend Paul Soliz ... and there was some sort of disturbance and someone called police, claiming a woman matching Britney's description was harassing and threatening hotel employees and guests. Officers showed up shortly after 10:30 PM, but they saw no signs of trouble and left.

We're told Britney and Paul retreated to a hotel room around 11 PM where they continued partying and drinking. While they were in the room they ended up getting into a huge altercation that we're told turned physical, according to sources, and Britney may have hurt her leg.

We're told Britney was screaming and "out of control" in the hallway of her suite, and several guests thought she was having a mental breakdown, so paramedics were called.

While we're told the call to paramedics was for a possible "injured person" ... sources at the hotel tell us they feared it was a breakdown.

Paramedics arrived around 12:40 AM. They made contact with Britney, who was walking out of the hotel with a pillow and blanket wrapped around her. She had clearly been crying. She did not get into the ambulance and ended up leaving with her security ... and without Paul.