Am i going crazy? is this normal?

is it normal that i think i'm mentally retarded or something? sometimes i feel like my life is just one big prank or something..and everybody feels bad for me and treats be good because i'm retarded..people tell me i'm a good singer and i'm talented and all..but what if that's not true? what if i'm just a retard and they're saying things so i don't find out that i'm actually mentally retarded? what if my school(s) are just mental institutions or schools for mentally retarded kids, but i didn't know..what if i'm actually like mentally ill or something and i just believe i'm not so in my mind, it doesn't seem like i am...what if none of my life ever happened..and it's just a figment of my imagination? what if nothing's real..and this isn't happening?..am i going crazy? :S I'm being 100% serious.. i think about this every day.. they say that the best people are mad..but i don't believe that... i mean..my school grades are decent..and i've never failed..but sometimes i just think reality isn't reality..i think i'm going crazy.. :/