I have a 1999 mazda 626 4cylinder and I was wondering if my transmissions bad

What is your question?

Whenever I'm in hill my car shakes and pops out of drive and reverses back and I have to push down on the gas so I won't hit and other cars and the same thing happens when I'm on a flat surface and it sometimes turns off on me and it constantly shakes when I'm stopped so can someone tell me if it's my transmission or not and would know how much it would cost to get it replaced