transmission seems to be slipping after only 46,000 miles

Ok i bought my 04' automatic SXT from a used car dealership about 10 months ago it had 35,000 miles on it an now it has 46,000. for some reason when i'm driving sometimes it just decides to stop shifting. and it sounds like my engines going to blow if i try to accelerate again. when this happens i have to pull over and turn the car off for about 5- 10 ins then it works as if nothing ever happened..... i have also noticed that when i keep the rpm's around 2000 it kind of goes back and forth between 2000 and 2500 rpm. also when approaching and leaving a stop sign/light it jerks....... and jerks bad! kinda like its backfiring or something. please help out if you know what is up i'm just hoping its not the tranny after only 46,000 miles on it. oh and yes i do like to drive fast as possible :banghead: