Usher‘s herpes accuser in Georgia, Laura Helm, insisted she ONLY had protected sex with him — even though she claimed otherwise in her $20 million lawsuit … but she had a good reason for lying, according to her attorney.

TMZ obtained a recording of Helm on the phone telling a male friend she had no plans to sue Usher after finding out he allegedly has herpes. She said Usher had always worn a condom when they had sex … so she wasn’t concerned about being exposed to the virus. As she put it … “That’s why they make protection, for people who have STDs.”

The conversation went down July 19 … just 2 days before Helm filed the lawsuit and changed her story. In the docs she said Usher did NOT use a condom when they had sex in New Orleans. The two different stories seem to create a huge credibility problem for Helm.

Her attorney, Lisa West, says Helm only lied because she thought her publicist, Dennis Byron — the guy on the phone — was trying to shop a story to the media about Usher having an affair.

West says Helm “didn’t want to be exploited and, in her attempt to deter Byron from doing so, she told him (inaccurately) that she never had unprotected sex with Usher and that she did not have herpes.” West adds she’s gone to law enforcement because Helm thinks Byron was extorting her.

Worth noting — Helm also accused Byron of stalking her, but on Friday a judge dismissed the matter for lack of evidence.