My 1997 GMC Sierra 1500 is not shifting right

I got in my truck this morning to leave for
work and put it in reverse to back out of
my driveway and just sat there and revved
up I've tried putting in drive and it seem
like you want to catch but he didn't move
then I put it in first truck started rolling
forward then I kept playing with it and
eventually the reverse talk going down the
road it doesn't seem like you want to shift
right the RPMs go away hi and then
eventually shifts what could be the cause
of this