Thanks for all the great replies.
Yes I'm very lucky she's so open, accepting and understanding. She really means a lot to me and I would never want to hurt her.
When she said I should get tested she said it would only be fair because I would expect the others to be tested and negative as well. At least that's how I understood it when she said it. We have actually never talked about condoms but I assume she wants me to use them. I guess that's something we need to talk about even though I think I already know the answer.
Going on PrEP is a good idea and I might need to do that. I plan on going to the clinic this week to get tested and I can ask about that too.
Here's what made me write what I did. I'm very glad she consented to me having sex with men. It opened up something I had kept from a long time. I finally felt free. I allowed myself to express my desires. I think that also led to me ordering the shirt as an acknowledgment of my desires. But while I've had sex with men the desire to bareback was never real, it was a fantasy. Ordering that shirt was as if that fantasy spilled over into reality. It's ridiculous, I know, but that made me freak out a bit. Because now there is this object that has my desire on it, plain to see. If that's what happens when I get horny, what's keeping me from actually going through with it?
The other thing that made me freak out a bit was that after finally being open with my wife and her accepting me as I am, I have something else that I keep hidden from her, quite literally. I'm scared to think of what happens when she finds that shirt. Back to square one. It feels like I'm breaking her trust. Which I guess I am. I'm still afraid about being open with her, for fear of rejection.