5 speed tranny, all forward gears, no reverse
 

I have a 91 f150 with a 5 speed. I was driving it around one day, parked(using reverse). Started driving again, went to park again, and it will not go in reverse. gears 1-5 work fine. It doesnt grind or anything, its just stuck, like not allowing me to put it in to reverse. The lights come on for backup but the shifter wont move any further.