By Michelle Roberts
BBC News health reporter
Sarah, 31, was sleeping with one partner and was taking the pill and using condoms when she contracted a sexually transmitted infection seven years ago.
"People don't have 'I've got an STI' written on their forehead"
"I started to get a sore patch and things got painful and I had a little look and noticed a couple of blisters," she said.
Weeks later, after a long wait to see a specialist, she found out she had caught genital herpes.
"I thought 'This is terrible, how can I have got this? I'm a good girl!'"
Genital herpes is caused by the herpes simplex virus, which also causes cold sores around the mouth.
Once the herpes virus is in your body, it lies dormant but may flare up and cause symptoms if you are run down or stressed.
It is passed on by direct skin contact, mainly during vaginal, oral or anal sex, or kissing.
Sarah said: "My GP was wonderfully understanding. He explained it is a really common virus and, although I had been careful and used a condom, it could have been through oral sex or because the condom had moved."
Sarah had to wait about six weeks to be seen by a specialist to confirm the diagnosis and check that she had not caught any other STIs.
"It can be a very embarrassing and humiliating experience. But is shouldn't be.
"You feel a bit naughty because you are there because you had sex.
"But it's nature - it's completely natural and everyone is at it. You shouldn't feel dirty.
"I remember being quite upset about the whole thing because I thought back to snidey jokes that I had heard years ago, like a pop star who had said the worst present a fan had ever given him was herpes."
She said she was relieved when she found out that she had not caught any of the other possible STIs.
She advised other people to be checked, even if they do not think they are high risk.
"People don't have 'I've got an STI' written on their forehead.
"But when ever you are sleeping with someone you are sleeping with every person they have had sex with and every person their partner has slept with.
"We should be going to get checked like we go to the dentist or the opticians.
"Most people do not wait until their teeth fall out or they walk into a wall before they think they need a check up.
"In the UK we have this ridiculous attitude to sex and sexual health."
Sarah said many people were put off by the long waiting times for GUM clinic appointments.
"That's got to change.
"I have spent all day sat in a GUM clinic. People don't want to have to take time off work to be seen.
"What do you tell your boss? You don't look ill."
She said better sex education would help and hoped government-planned safe sex advertisement campaigns would send out the right messages to the right people.