Everyone's level of comfort is going to be different and should be respected. That said, make sure you understand the real dangers and not just what you think they are. For instance, at one time I was worried that my partner's partner, who's a sex worker, was at risk from having unprotected oral sex with people whose STI statuses she didn't necessarily know.
Then I actually looked up rates for transmission for various STIs via oral sex, and discovered that the things that can be easily passed on are curable, and the things that are incurable and scary (AIDS!) are virtually impossible to catch via oral unless you have an open, bleeding wound in your mouth, and even then are difficult to transmit. That left HPV and herpes, both of which ARE easy-ish to transmit via oral and ARE incurable. HPV was no big deal to me -- I've already had it, and am vaccinated against the other strains.
So I had to decide, was I scared of the one thing left, herpes? Did I consider that risk an acceptable risk? I did a lot of reading, and eventually decided that it was a risk I was taking already, constantly, with other partners, and that it wasn't actually that big of a deal (basically, in healthy people, an occasional skin condition in an embarrassing place). I surprised myself with that way of looking at something that had always freaked me out so much in theory -- in the end, the big scary monster just wasn't particularly scary.
All of that info, combined with knowing my partner's partner's safer sex practices (talking to clients, always using barriers for PIV and PIA, and getting tested every three months) led to something I never would have expected a year ago -- I'm now fluid-bound with someone who's also fluid-bound with a full-service sex worker, and I'm not worried at all (and I'm a chronic worrier!).
Anyway, that's one person's story of facing the question of safe sex vs. fun sex and making an informed decision. If my decision had gone in a different way, or if yours does, that's ok too, as long as you've really considered it and end up with something you're comfortable with. It was hugely important to me that I be able to make a free, unpressured choice. My partner made no secret that he was interested in fluid-bonding. I, in turn, made it clear to him that that option would be OFF the table if I felt like it was something I *had* to do to make him happy. You can't think clearly under pressure.
One more thing, fluid-bonding is no light matter to me. I've seen other people say things above like "can't you just trust your partner to have un-barriered sex with people they've known for a while and feel comfortable with and who use good practices"? I think that's unfair. With every single non-monogamous person who's added to your circle of fluid-sharing, your risks increase exponentially. That's just math. It's ok to be worried about it. It's ok to be careful. It's ok to not want too many people to be in that circle with you. It's ok to not want ANY to be in there with you!
In the end, safer sex CAN be very, very fun sex. There are a million and one things you can do that involve minimal risk and that bring pleasure and connection. Don't let anyone tell you otherwise.