Yeah those rapid antigen tests are too often false negatives.
Funny that you mention B12 and Iron. My wife went to the store three days ago to get some for me. Why? Friday night, my restless leg syndrome was off the charts, actually preventing me from getting a good night sleep. Saturday morning, my sickness began. The wife did some digging and found that B12 and Iron might help with restless leg. So now I'm taking a pill that has iron, B12 and folate.
I should mention that I supplement daily with Vitamin D3, about 3000 IU (summertime), but for about 10 days before I got sick I had run out of pills! (Coincidence?) So when my wife went out to get the Iron and B12, she also got the D3 for me, which she also read might help with restless leg. Of course I also supplement with magnesium biglycinate, vitamin C and A, zinc and NAC hehe. Also, I started taking Quercetin and melatonin when my symptoms started.
PS For anyone wondering what restless leg syndrome is, it's a persistent, achy, unpleasant crawly sensation in the legs, mostly lower legs. I've had this since I was a kid but only a few years ago I learned it was a 'thing' and had a name! People marvel that they seldom see me walking, I'm almost always running at various speeds. This is because running gives me some relief from the restless leg. Walking doesn't.
For that restless leg, I heard that infared treatment shows great promise and I myself would try a tens machine for electrical stimulation and vibration