Automatic tranny won't shift
 

I have a 2010 Mitsubishi lancer while driving 55 mph the engine started to get louder as if I was manually in first gear the tachometer was between 3 and 4 I pulled over and shut the car off. Starting it again I could only drive less than 20 mph to get to my destination making sure the tax did not go over three. While driving home again less than 20 mph took me an hour and a half to get home normally 20 minute drive any suggestions?