Trans/overdrive on 93 not engaging and has hard shift???

I have a 1993 Camry LE auto, four door with about 117k miles. Recently I have been having problems with the transmission shifting quite hard into the last gear. So going down the freeway at 65mph at 3500rpms and dropping my gas mileage from 24 mpg to 19 mpg. I was just curious to know if anyone had any ideas what the problem is. Thanks for your help and any ideas would be appreciated!!

By the way I am a college student so I am trying to get an idea how much this is going to cost me to fix since I am on a tight budget.

Get yourself a fluid change. A lot of times it won't shift into O/D because it's low on fluid.

Or just needs fresh fluid. Stuff sticks when the lubricating quality of the ATF goes away, which it does. Like jsinton said, definitely flush the tranmission - replace the filter if you have the resources.

Thanks so much. I am glad it is not something too serious. I appreciate your help.

Nobody said it wasn't serious... you just need to perform certain steps to see if it is serious or not. In other words, don't drive around too much until you change the fluid, sounds like you already fried your trans.