Isuzu Ascender won't shift into gear when driving

I just replaced the battery on my 04 Ascender and for the past week, whenever I drive it it struggles shifting into the next gear and when I come to a stop, it barely moves and starts jerking before finally shifting into the next gear. I practically have to floor it to get the car to move. Feel like its gonna stall out at every light and then after I get it going, it eventually shifts while the RPM's are all over the place? Seems like its getting worse by the day. Any help or suggestions? Thank you!