Michael Lohan's ex-girlfriend told police ... he flipped out and threatened to kill her because "she wouldn't give him a 'bl*w job'" ... this according to the police report obtained by TMZ.

According to the report, Lohan's ex, Kate Major, told police Michael came over to her Tampa apartment last night, when he began to yell at her about an upcoming domestic violence court hearing. Major claims the argument got heated ... and MiLo got violent.

Major claims Lohan pushed her multiple times and squeezed her arms. She claims Mike also told her he would "slit both his wrist and her wrist. He also threatened to throw her off the balcony (4th floor)."

Kate says Michael threw a TV  remote control at her ... but he missed, so he smashed her cell phone.

Major also told police Lohan came over to her apartment the night before ... and they got into an argument that turned physical. Major says she threatened to call police, but Michael banged his head on a door, causing his forehead to bleed ... and warned that if cops came over, he would blame her for the injury.

Major told cops she regretted not calling police at the time, but insists "she was scared."

Lohan also spoke with police ... insisting last night's incident was triggered by a sexual encounter ... described in graphic detail in the police report.


"[Kate Major] did not want Michael to ejaculate inside her. Michael Lohan stated he did ejaculate in her and his girlfriend got very angry."

Michael told cops Kate told him she may have been pregnant from previous sexual encounters with him ... which caused an argument ... but Lohan insists he never laid a hand on Kate.

Michael also told cops the cut on his forehead was caused by Kate ... who slammed her apartment door in his face on the previous night.

As we previously reported, Lohan complained of chest pains ... so cops took him to a nearby Tampa hospital, where he was treated ... and then arrested for domestic violence.

Lohan claimed in his statement to police that he and Kate were going to court today to drop a previous restraining order that was in place against him. We're guessing those plans have changed.