Am I stupid?

I recently attended training session at my place of work on data analysis. In the final exercise I scored much higher than my partner and some other people in the group. My partner believed the final test was much simpler than the previous ones. She asked me if I got everything right too and immediately said to the group that she thought the answers were intentionally made to be very straight forward. I couldn't help wonder if she thought I wasn't bright enough to pass the test.

Also I'm a lot more aware now that my thinking ability has slowed down. I've been at the top of my class throughout high school, my undergraduate studies and postgraduate studies, including receiving awards. Ever since I moved cities to start my new job, everything has changed, I've lost my self confidence which I blame on having a boss and colleagues who constantly put me down for even the smallest errors- I once received criticism for saying "thank you" too often. I always know if I do 98 per cent right, my work will be belittled for the 2 per cent I got wrong.

At work, in group settings, my contributions are quashed by colleagues, but if someone else in another group says the same thing, it's supported. I'm convinced my environment has made me lose confidence in my mental ability because my boss constantly focuses on my flaws, sometimes with a condescending tone and also because I've grown increasingly afraid to approach people. The latter is because I only ever seen myself getting yelled at, sometimes for really minor issues. For example once I commented during an informal discussion that winter had come twice that year- I didn't mean it literally. That year we had heavy snow fall for a long while, then a long dry sunny spell before it snowed heavily again. I was rebuked very sternly for not getting it right. My colleagues raise their voices at me if I ask them questions about anything, whereas they ask me the same types of questions and I'll readily help.

Also, I get aggressive glares from one particular manager for things that other people easily get away with, I'd much rather receive a vile verbal insult than the way he looks at me but I just look down until he stops, the whole while, I can feel him looking at me as if I was the worst criminal that walked this earth or dog-poo under his shoe. I recently had to work with a supervisor and a colleague on a new system. Another supervisor would dismissive anything I said and rebuked my work for things I had not done which he thought I did without actually looking until he learnt that I had been more productive than my colleagues.

Their behaviour doesn't align positive feedback. On one occasion, things got so bad I started to contemplate hurting myself. Soon after, I was put on antidepressant medication by my doctor.

I can't help wonder how I've contributed to the situation. Noone tells me, they don't write it in my reports, I've only heard that I'm not always smiling. But how can I when my cortisal levels reach the roof the second I step foot in the building? The only way I can get through the day and go to bed at night is if I stay silent all day, otherwise, anything I do is a call for a verbal lashing. Yet I can't deny that my experience in this environment has taken its toll on me mentally. I sometimes find it hard to put sentences together, even remembering names, or words is taking a lot more effort now.
I sometimes have to ask people to repeat what they said before I can respond. Before, I could read pages of a paper once and present it clearly to a group.

It hasn't helped that I'm too tired after work to consider a social life. It felt so good the other day for someone to ask "How are you?" and really mean it. I actually welled up a little and wanted to hug the person.

My purpose in writing this is I'm wondering if there's something seriously wrong with me. Am I dull? Am I slow mentally? Does it make sense for me to feel less smart because of the relational experiences I've had at work? Will I ever return to my old quick-thinking self or should I resign to more routine jobs from now on? Or will changing the work environment help? Is there anyone out there who's experienced similar or am I making a mountain out of a molehill?

Sorry this is so long.