The reality TV personality made the claim during an appearance on RTE chatshow The Saturday Night Show over the weekend.
Houghton told host Brendan O'Connor: "I didn't break up with Alex lightly. I was with him, we got married - married? We got engaged - I wanted to be with him, I fell pregnant.
"Things happened during that pregnancy, but ultimately, a man ended our relationship, and that's all I'm prepared to say."
"A man? OK. And you're not talking about Alex?" O'Connor asked.
"No," she replied.
Houghton also said that she did not know about Reid's drag alter ego Roxanne before they got together.
She said to O'Connor that she was told Roxanne was "a publicity stunt [and] a joke", and that she only found out this was not the case when she was pregnant with the couple's daughter Dolly.
Houghton broke down in tears during a recent appearance on This Morning, saying that she was finding her split with Reid "really tough".