I change filter and fluid 3 weeks ago. Got in to go yesterday and it was like slipping and it got better as it warmed up. Got two miles down the road turned it off got back in it and it would only go in reverse. Finally it started to go giving it RPM and then it would just rev up and all I had was reverse again. Got almost home and it didn't even have a reverse then it completely went out. Set and fooled with it taking it in and out of gear till finally got reverse again and then backed up the rest of the way home. What could this be?