Posh wanks aside, here are my thoughts on the situation.
I agree with the posters who think the condoms were probably given to him by a sexual health clinic, and I think your time frame of Christmas 2023 (based on the unworn jumpers and the expiry date on the condoms) is probably accurate. I doubt the condoms were deliberately hidden away in the laundry room. Your husband could just buy them as needed, or keep them hidden at work. I'm guessing he was given these by the clinic to use with his wife, while waiting for test results to come back on an STI. (Or waiting for a course of antibiotics to take effect.)
The box wasn't a hiding place. He just put them away and forgot about them. Then muddled them up with the unwanted jumpers later. It was easy to do because he never planned on using them. That would mean telling you the truth, and he had no intention of that. And he wasn't getting his end away at the time, when he'd just been burned, so they were irrelevant on every front. Out of sight, out of mind. I don't think putting them back will tell you anything in this case. I'd bet money he doesn't know they're there.
I also doubt he would have gone to the clinic if he wasn't showing symptoms of a sexual infection. Was there a period of time where he was uncharacteristically disinterested in sex for a while? If so, it's likely he was on a course of antibiotics and didn't want to have the condom conversation with you. I echo the suggestions to get tested ASAP, OP. There are plenty of STIs that show no symptoms, and he may have thought he got away with it in the past.
I'm sorry this is happening to you. You deserve better. No ifs, no buts. You do 🌺