Is it common to go through hours or days of tests only to be told "I don't know what's wrong with you."?

Often. So many symptoms, or collections of symptoms, are common to so many, varied, medical issues.

I hope you feel better.

Yes.

They would figure it out if you have a good internal medicine doctor running the show. What you say is common, but it’s a relief because it means they have ruled out many horrible possibilities. My aunt got plugged into the medical wheel and they never found out what the problem was. She just got tired of riding so she disembarked, went home to carry on and her symptoms disappeared. You never know. You have to proceed based on your own instinct.

I took a new approach about my medical issues recently, and I think I am on the right track to get help at last.

It started with the movie Awakenings.
I love that movie, and had already seen it multiple times. However, watching it again a few months ago, I decided to do a search, and see if that brilliant doctor still lives.
He has passed. There was a listing of his books, and one caught my attention because it seemed too absurd to be real. I thought it must have been some sort of comparison double talk.
The title is The Man Who Mistook His Wife For A Hat.
I ordered the book.
The title was for real. The book is fantastic. It had all sorts of patients described with all sorts of neurological issues.
Some had been diagnosed as schizophrenic, others were unable to get any diagnosis at all, until they were seen by him.

Reading the book cleared my thinking on a few things. Some doctors have only a basic knowledge of medicine, and aren’t really qualified to diagnose much. Some conditions can mimic other concerns, and make diagnosis quite tricky.
After reading the book, I gained new resolve to research my symptoms, put more pressure on my primary physician, and ignore the shrugged shoulders.
We are now getting somewhere.

I had gotten so frustrated with one doctor after another saying they couldn’t cure all my issues in one appointment, and tell them what is bothering me most right now.
Pfffft!
I can’t seperate my symptoms into seperate categories! If I knew what goes where I could fix it myself.
So, I did searches, changed the wording because that for sure helps to get new subjects to pop up. Finally I did it. I found something which fits me exactly.
I told my doctor and she said no, that isn’t even a real thing. It is just one of those internet diseases made up to get people to spend money.
Well, it is a thing. It is rare. I may not have it, but if I do or don’t, it got the ball rolling.
I pressed her to order the blood test which can usually determine this condition.
My doctor contacted me later to tell me she did have the test run from the samples drawn that day, but she wasn’t qualified to read the results, so she sent them to a research hospital with a terrific reputation.
An appointment was set up. I had to wait almost two months, but I finally went this week.
Lots of questions, and a painful exam later, I was told I would be given an appointment in a couple of weeks to get a bunch of tests and lab work done.
Maybe I diagnosed myself correctly, maybe I’m a bit off, but it gave my doctor a jumping off point to get me seeing the right people.
After eighteen years of constant pain (other than my kid), and deteriorating health, I am finally on the right path.
In the support group I joined for people with the condition I likely have, and patients waiting for diagnosis who also share same or similar symptoms, all were either misdiagnosed in the past, or told it was in their heads, or the good old shoulder shrug.
Some conditions and diseases are real buggers to figure out, and if rare, then few doctors even know what the symptoms are pointing to.
Yes, lots of people have gone through repeated testing with no answers.
Some never do get the right answer.
Persistence is key.

I had daily weakness and real fatigue then read some guy who said he stepped up his water intake and all his symptoms vanished. It works. My tiredness is gone. I still have this not that uncommon “walking on marbles” on occasion but I’m not going through a battery of tests!
@Patty_Melt that was a very uplifting, encouraging reply. I’m happy for you!