Having sex with someone that is having sex with other people increases your risk for catching STDs.
As AJ said, he could catch HPV, herpes, and syphilis and bring it to you. He is very WRONG. He is so wrong that you have to wonder if (a) he is stupid, (b) thinks you are stupid, or (c) just does not care.
He should be responsible and get tested regularly, at least once per year. You should too.
1. Have you been tested and vaccinated for high-risk HPV? You should discuss this with your doctor? If you do not have a doctor go to Planned Parenthood.
2. You should insist on using condoms with him if you continue your relationship
3. You should watch for signs of STDs. You should check to see if he has blisters, sores, or discharge before engaging in sex, protected or not.
Women have an elevated risk of catching STDs. You should be careful and protect yourself. He is not helping you with that.
No, that's not true.
You can get HPV, herpes and syphilis when using condoms.
Is he using condoms with you? If he's not, what makes you think he is with the other woman, and why would you be with someone who is sleeping with someone else and doesn't respect you enough to test?
AJ