She fled for her life after he began to throttle her, but later suffered a miscarriage.
Her vision had started to blur after she was doused in bleach, which ran down her face and neck.
Declan Johnston (24) of Bo’ness, pleaded guilty to assault, police assault, threatening behaviour, criminal damage, and theft.
Stirling Sheriff Court heard how he screamed “I’ll kill you” at girlfriend Kelly Wilson (22), then pregnant with their baby.
Prosecutor Cheryl Clark said: “He pushed her onto the sofa before putting both hands round her neck and strangling her.
“She could not breathe.”
She had to climb out of a smashed pane of glass in the locked back door before fleeing half a mile to the McColl’s shop in Dean Road, Bo’ness, pursued by Johnston.
There he wrecked the shop and attacked the 60-year-old shop assistant and a customer as an 80-year-old co-worker looked on.
Shop worker Elizabeth Rennie (60) reminded Johnston he was already barred from the store, after previous incidents when he was drugged or drunk, and said she’d called the police.
Johnston replied: “If you’ve called the polis, I might as well do it right” and began to tear down shelves of drink, condiments, and greeting cards, while smashing bottles.
Swigging from a stolen drink can, he pelted a customer who entered the store unawares with bottles, jars and cans, and flung a can of beer at Miss Rennie as she tried to make a second call to police.
He threatened: “I know where you stay, I’ll find you and set fire to you.”
Then he walked out with a case of Stella Artois under each arm just as two marked police cars arrived.
Saying, “Oh, here we go”, he began to throw bottles of alcohol at the officers.
Bottles landed at their feet and smashed, but one officer was hit on the head.
He also threw bottles at a police car, smashing the windscreen, before retreating back into the shop.
One cop managed to grab his arm and pull him out of the door, but was punched, kicked, bitten on the forehead and headbutted by Johnston, who was “lashing out and making unspecified threats”.
A policewoman used incapacitant spray against him, but it had no effect.
The court heard it took at least four officers to subdue and lock him in a police van cage, where he ranted and made gestures.
The incident, on October 30 last year, began after Johnston produced a bag of tablets and swallowed up to 20 of them, stashing the rest before falling asleep.
He woke at 9pm and began to look for the bag of tablets, turning on Kelly when she said she didn’t know where they were.
After striking her on the face he poured bleach, chilli sauce and tomato ketchup on her and tried to strangle her - then eventually let go, and began “wrecking the house, looking for Valium”.
Miss Clark said Kelly, “panic-stricken and desperate to leave”, ran towards the back door - but had found it locked, with no keys in sight.
Johnston told her she could leave if she wanted to, and smashed the glass in the door with a dumb-bell.
When she escaped into the street he followed her to the McColl’s outlet and said “I want to talk to you” before trashing the store, causing an estimated £13,000 worth of damage.
Johnston’s lawyer, Simon Hutchison, said pills - said to be made in a “Breaking Bad” Paisley drug factory - had caused him to “completely lose control of himself and his surroundings”.
Mr Hutchison said: “This was caused by Mr Johnston taking pills which he thought were street Valium, but turned out to be ten times stronger pills called etizolam.
“This wasn’t known to him at the time”.
Sentence was deferred for reports and Johnston was remanded in custody.