Yeah, and "gay" used to mean happy, too.
Has no one spoken to you at all about what's going on? Given you a label to hang this stuff onto, an idea to research? Because when you don't have that, you tend to jump to the conclusions that I see written here: I Must Be Dumb.
Instead of asking your parents and teachers "Am I dumb?", try asking them, "What am I diagnosed with? What have I been tested for? I can tell there's something going on, just let me in on the secret!"
When I was growing up, I didn't get a label. Instead, I got told that I "Wasn't trying hard enough," that "I could do better than that," and all kinds of B.S. It took me until I was 16 to figure out what was going on, that it was a variation of dyslexia. These are bits and pieces of a video that literally put it all together for me; you can probably find it in the library.
http://www.youtube.com/view_play_list?p=86BCBE9D53BDA766
You can't GET into Special Ed without some testing having been done. You have scores and a diagnosis floating around somewhere. Demand the truth, tell them you want to know, cause all you're being told right now by your peers is that "you're dumb."
You may not have dyslexia. You may have a hearing or processing disorder, there are dozens of things you may have going on. But if you can understand it, you can get a better grip on it.