Lately I’ve been feeling stupid. I have no intelligence at all. Ever since I was a kid I couldn’t pick up things as quickly as others. I’m not as sharp and quick as everyone else. Family would yell at me whenever I couldn’t do a task correctly or if I asked a question or two about it. I’m 25 now and even to this day it happens. Today, I had to help my brother with loading something onto his truck and I didn’t push it far enough. He yelled at me and even when he thanked me for the help I still felt stupid. Even at my job I feel so lost at times it feels like I could lose the job. I try my hardest to understand things and learn but I just can’t. And even if I do it took me so long just to get even the basic stuff down. It’s getting to the point where I feel useless in life. I don’t want to be a genius but I want to be smart enough to at least get by without being yelled at or treated like a dumb child

You seem to have self awareness at least and you're probably not as brain dead as you think. Your internal thoughts of yourself are really important to how you react to situations in the real world.Peoples negative remarks overtime can compound over time into you perceiving yourself as in this case "stupid" and cause a snowball effect. This might sound retarded but what you eat/don't eat is also so important to your cognitive ability. As a last resort maybe talking to a doctor and or doing research to see if you might have ADHD or something you can receive help for. Regardless of what you decide remember the more you think of yourself as "stupid" the more you will act "stupid".