What do think about my reaction?

Hello all,

finally I've decided to start with Lugol 2%, Solgar selenium selenomethionine. All the other co-supplements I've been taking for weeks already.

So yesterday evening I took 100 mcg of Selenium. During a while I felt nausea. I decided to go to bed and sleep.
In the morning I woke up and suddenly I felt a sharp pain in
my thyroid. It was very short pain like 3 seconds.
I ate my breakfast and took only 1 drop of Lugol. I also took my morning vitamins including vitamin C (I know now it is not good).
During a while I had strange feeeling on my back/neck. My neck was blocked and I felt nausea again. Nearly whole day I was feeling like a crap.

I don't take any medicine for thyroid and according my doctor I have no thyroid problem but I have some hypothyroid issues like cold hands, fatigue, anxiety. In the past I used Kelp without any problem.

Any idea what could be a problem, please?

Thanks a lot.