1993 Toyota Camry I'm pushing almost 4,000rpm at 60mph.

My car was working just fine a couple of days ago. I haven't done anything to the car to damage it in any way. It seems like all of a sudden it just started acting up. When I'm driving from my home I have to get on a highway as soon as I leave my driveway. For some reason it just won't switch gears, I'm almost pushing 4,000rpm at 60mph. My car has had a history of problems such as the timing belt breaking and a major oil leak. The timing belt has been fixed and replaced and the oil leak has been sealed somewhat. So, please get back to me as soon as possible, it would be greatly appreciated. Thanks.