right now my transmission is getting rebuild. I had similar problem and it just got worse with time and to be for specific I was having the exact same problem with the transmisison changing from 2nd to 3rd it would take forever and it got to a point that it wouldnt shift at all at times.
just be ready to spend $$ because ur tranny is done for sure.
I am getting mine fix at this place. they charge me $1600 for a rebuild plus new converter and they even gave me a free rental car until the fix my car. http://reliabletransmissionsltd.com/index.html