Weakness and thyroid question?

Well, I’ve been to the doctors and still have to see a neurologist in a couple of weeks for my medical problems. I won’t mention them except one, but if your curious you can browse through my health questions(ignore any weird questions as I was drunk when I asked one lol)

Anyway, I know it should be obvious, but I don’t really know.Twice my doctor asked if I’ve been experiencing muscle weakness, but I don’t know.

A few times my legs have become heavy to the point I need to sit down and thats with little walking.

Another thing is last thanks giving I was holding a paper plate of food(obviously not heavy)with my right hand and I felt fine, then suddenly that arm went numb and went limp for a few seconds and I had to set the plate down before I dropped it….Are any of these signs of weakness or what?

Also, my doctor said it sounds like I at least have a thyroid problem, but he said they tested me for it before and I wasn’t so I have my doubts….Can you please name any conditions that have symptoms similar to thyroid problems? Preferably common, treatable conditions, because I know I don’t have anything chronic/

I’ll just add that currently my legs are heavy and aching right now.
Sorry forgot to add I am 21 years old and I am average weight.