Need advice UPDATE

So my bf told me that he wants to do something similar to swinging... like with another couple.. he described it as we start having sex with each other then we switch. He claims it isn't cheating bc we would both be there...

But idk how I feel about this..

What do u guys think????

He said he just wants to try it. So I'm guessing he means a one time thing. But there are some major concerns:

Does this mean I'm not good enough for him??

Also he hates condoms. I mean literally refuses to use them so. Like ya what about that??

And what happens if she gets pregnant?

Or how about STDs??

Ugggggg idk I'm worried if I say no our relationship is going to die but at the same time something like that could kill our relationship to..

Idk