So normally when i drive my car(which is a mazda 626 LX 2000) it doesnt quite change gears smoothly. it also hesitates when switching in lower gears. But yesterday when i was driving to work. car seemed normal until i got to an intersection. My car was stuck in 2nd gear. then when i pulled off to the side of the road. I turned it off and turned it back on. It then was stuck in 1st gear. ( i could still reverse) [Also when ever i switched to reverse or park or neutral i could feel it jerking hence it shifting] I would be able to go in 1st gear, the car would move a little but the speedometer was stuck on 0 and my car would rev like a crazy. I checked the transmission fluid and it seemed fine. The thing is today i checked out the car and i tried shifting from park to reverse and i could still feel the shifting(jerk) but once i turned it off and turned it back on. i was not able too. i couldnt reverse.. (b4 when id shift into drive the car would move forward a bit but wouldnt accelerate). NOW it wont move at all. and all it does is rev even when im pressing it a lil.

Once again my car is a Mazda 626 LX 2000

2.0L 4-cyl. engine; Automatic transmission

Do i need to buy a whole new transmission? or maybe its the speedometer cable?

 

From what I know about them, and I am sorry to have to say this to you, those years are the worst for the auto transmissions. For what it's worth, Honda/Acura was having a similarly hard time and did very little for their customers. Every 30-40k miles they need a new trans.
My best recommendation is to DUMP THE CAR ASAP!!! The other less plausible option would be to find a junk donor car and convert yours to std shift.

 

If I am correct these cars have a version of the CD4E transmission that is also used in Ford Contour/ Mercury Mystique/ cougar models.

look at this video: