The Celebrity Big Brother 2006 winner described the former cage fighter as "rotten to the core" in her first interview following an emotional Twitter outburst last week.
Speaking to The Sun, Houghton claimed that when she was eight months pregnant, she came home to find Reid watching porn while dressed in her underwear.
"The shutters were down on the whole house, it was dark, but there were flashes of light from the TVs," she said.
"I went upstairs and it had been turned into a sex dungeon. My underwear was all over the landing. Then I walked into the bedroom and saw Alex dressed as his alter ego Roxanne - in stockings, suspenders, a red wig, make-up and heels.
"He had pierced his ears with my earrings and they were bleeding. He had my false eyelashes on and there were sex toys all over the room, with porn playing on the TV.
"He looked off his head. I believe he had been taking legal highs. His eyes were glassy and wild. He was staring, as if in a trance, and was dripping with sweat."
Houghton added: "The place stank of smoke - he only ever smokes as Roxanne - and just grossness. I don't believe he would have even known I was there."
After her encounter with Reid, the reality star said that she left their shared home in shock and slept on the floor of her flat.
"I was so embarrassed I couldn't go to friends or family," she claimed. "I went back every day to see if he'd stopped and feared he'd be dead.
"I begged him to stop but he kept saying how horny he felt and asked me to perform a sex act on him. I even found Alex wearing my wedding ring from [ex-husband] Preston and another ring I was given by someone special.
"I will never forget what I saw. I'd just finished [their daughter] Dolly's nursery. There was her cot and her clothes, and next door all this was going on.
"He told me he was really sorry, scared, and would never do it again. He said he would get help. I felt vulnerable and didn't want to be a single mum.
"I fell for his story and here I am, the mug, sitting here. I lacked the strength to leave."
Reid and Houghton met in April 2011 and got engaged in October of the same year. A month later, they announced that they were expecting a baby and Houghton gave birth to Dolly in June 2012.
"I am so relieved we didn't marry," she said. "He put me through hell. I'll never forgive him, he's rotten to the core."
The reality star revealed that despite things ending badly, she will still let Reid - who was previously married to Katie Price - have contact with his daughter.
"I didn't really see Alex as a dad, he was never around," she said. "He's bought her a few bottles and a babygro and offered me £50 a week but drives a car that cost over £1,000 a month - and I've found a receipt for £500 for sex toys.
"Yet he's Dolly's dad and that's their relationship. I haven't stopped that.
"I don't miss Alex at all. I miss what my life should be like. But Dolly is amazing, I'm so in love. She's such a happy little girl.
"For now, I've got to concentrate on giving Dolly the best life I can."