Automatic transmission shifting issue

I have a 94 Mazda B4000 4L 4x4, it was running fine until last night when I was driving along and it droped a gear, hard, and didn't want to shift back up. Now when driving it will red line itself before it will shift, and to get it to shift I have to get up to speed, let off the throttle and it may shift and if it doesn't I have to give it some throttle and lay off again and it'll usually go into gear, sometimes hard. I'm not missing any of the gears, my tranny fluid is full, and besides the shifting issue the tranny seems to be working fine. So I'm thinking it may be some sort of sensor.

Also, as long as I am just putting around it doesn't seem to have the problem as bad. putting around means just barely on the throttle with little to no acceleration, under 30-40 kph, 10-15mph.

Thanks