2000 Toyota Camry Any ideas what could be wrong with my tra

A few days ago I got in my car and Reverse would not work I put the shifter in position but when I push the gas it acts like its in neutral. Unfortunantly I can't stop driving it because I have no other way to get to work so I drove it home and back to work the next day this time when I went speeds over ~45 when I let off the gas the RPMs drop to ~1k and it acts like its in neutral when I try to accelerate untill the RPMs go to between 2.5-3k depending on how fast im going then it seems to "catch" again and I seem to be driving normally untill I let off the gas again. Any suggestions or ideas on how much it might cost to get this problem fixed?