Sorry to say this sounds like the transmission has an internal problem. It may need to be repaired or replaced with a rebuilt transmission depending on the condition and mileage. I suggest taking it to a shop and have it inspected, try an ATRA shop, they are really knowledgeable about transmissions. http://bit.ly/ATRA_Info Good Luck!
Thank you so much bretb. I was told it was my transmission but I didn't want to believe it because it goes forward. I was also told that I could get it rebuilt versus get a whole transmission. The car has alot of miles.
This is a fairly common symptom when a transmission fails, so it sounds like a correct diagnosis. I suggest you look into getting a re-manufactured transmission with at least a 3 year warranty, these are quite common at good transmission shops.