So I'm dating this girl (25F) who has been with multiple men as she used to hookup a lot during the past year, nearly every other day. I don't know how many of them were protected or unprotected as I didn't find it appropriate to ask. I (28M) have had 3 sexual partners till now and have had protected sex will all of them. I want to ask her to get herself tested for STI once so that I can be sure that it doesn't get transmitted to me if I perform oral on her. I can't think of putting it in a way that doesn't come off as judgemental or feeling like an asshole. How can I put it in a way that it doesn't come out as judgemental?

Edit: It's not going to happen. She went out and hooked up with someone again yesterday. I'm going to call it off.