The glamour model and former Big Brother contestant revealed that she is three months pregnant and told The Sun that the news has "transformed her life".
"I can't believe how happy I am," she said. "What happened last year was utterly horrendous.
"I never thought I would find happiness again but finding love then falling pregnant has transformed my life. I can't wait to be the best mum I possibly can be."
Thomas gained notoriety in 2011 after footballer Ryan Giggs sought protection against reports of their extra-marital affair with an anonymity injunction. After weeks of speculation in the media and on social networking sites, the order was broken by MP John Hemming and Thomas was cleared of allegations she had blackmailed the Manchester United star.
Following the revelations, Thomas was subjected to verbal abuse on the street and suffered death threats on Twitter.
"Last year was a nightmare. Now I'm the happiest I've ever been," she said.
"I am now 12 weeks and am due in January... I have been trying to cover my bump with baggy clothes but my boobs are growing huge too and I think people are starting to notice.
"I'm really excited to finally come out and say, 'I'm going to be a mummy'."
Thomas and city trader Horsley began dating last year, despite prior claims by the model that she wanted to stay single.
"Adam and I have been together for just ten months. It has been a whirlwind but when you are in love I don't think it matters how fast or slow you take things," she explained.
"After having the baby... I plan to get my figure back as fast as possible and get back to work. But I would like two, maybe three."
Thomas added: "I will tell them all about me - the good and the bad bits. They are all part of my life. I don't regret things.
"I don't see the point in regretting. But I am happy that I am in this place in my life now."