On June 4 - eight days after he popped the question to Jillian Harris on The Bachelorette finale - Ed Swiderski slept with former girlfriend Lindsey Johnson, according to the new issue of Us Weekly (on newsstands now).
A day later, he tried to bed a different woman, Bethany Steffen, texting her to "bring beer and condoms" over to his place, Steffen tells Us.
The humiliated women are speaking out now to warn Harris, 29, about her new fiancee's two-timing ways.
Says Steffen, "Ed's not worth my time, but if I can help someone avoid heartbreak, I'm gonna do that."
According to Us Weekly, Swiderski had been dating both Steffen and Johnson behind each other's backs prior to filming The Bachelorette in late March (the finale, taped in May, aired July 27).
Even while he was on the hit ABC show he texted Johnson that Harris wasn't his "type" and that he prefers "all blondes," she says. "I love you," he also wrote her.
Us Weekly reports that he lied to Harris when he said he had to bow out of episode five because he thought he'd lose his job as a Chicago Microsoft consultant.
While away, both women say they slept with Swiderski.
He then told them he was off to "a business trip in Texas," when in reality he returned to film episode seven of The Bachelorette and declare to Harris that he had "reprioritized" when it came to work and romance.
Of the women's claims, Harris tells Extra, "It's not possible... This is a bump in the road and we'll get through it."
But Steffen warns Harris, "Lindsey and I are both smart girls, and Ed just has this way of making people believe what he wants. Jillian needs to be careful."
Adds Johnson, "I feel gross, used and completely violated. It shocks me that he was able to do something like that to me."
For more on Swiderski's cheating ways - including his steamy e-mails to Steffen and Johnson, how he promised to propose to Steffen by year's end and how he badmouthed Harris while filming The Bachelorette - pick up the new Us Weekly today!