Transmission problem, 98 gmc sonoma, cant figure out what is wrong?

i have a 4.3l gmc sonoma with an automatic transmission, and i was driving it around, everything was fine, wasent in 4x4 or anything, and i got it to 5000 rpm and it will usually shift and not go any higher, but it dident shift and the rpms almost got to 6000, parked it later at a buddys house and later found out i dont have reverse anymore, and when im driving it wont shift, i have to let off the gas when im at about 20 mph and it will shift, same when i get to about 40, etc, and i cant hit the gas very hard or the rpms jump to about 4000-5000, i checked my fluid and it seemed to be dry, i added fluid, and problem still persists, im guessing i grinded the **** out of my gears or something, im hoping thats not what it is though, any ideas on what i need to replace, thanks