Yesterday 2 times separate times, when i put it in reverse and pushed the gas to go in reverse it didnt go in reverse, so i had to put it in park and back into reverse again, why did this happen twice anybody know? Do i need to change my transmission fluid or something?

 

sounds like a worn out clutch or pressure plate or it could be low fluid pressure. just sayin this off of speculation i could be wrong but these sound like very probable causes

 

Also sometimes but not all the time, when im driving and its about to change gears, it kicks into gear, and also sometimes right when i press the gas to go it give a little jerk just a small jerk like the transmission kicks into gear also

 

My truck does this same thing! 2002 2500HD. it feels like transmission kicks in gear when i hit the gas after ive been coasting and it also did the reverse thing once.

 

Ok i had the same thing. GM transmissions have an issue with this
They are made with weaker parts like polyurethane and hard plastics, and they tend to break or wear out. So you may need a new transmission, check first with a good shop. As for your hard shift you can fix that easily. Again with GM the slip yolk on the driveshaft was a bad design. All you need to do is take out the rear driveshaft and grease the slip yolk. Then to prevent anymore hardshifts, as you will have to grease monthly or buy an aftermarket slip yolk, I would buy a shift kit to reduce the torque on your driveshaft between shifts because it will shift much faster or smoother