Originally Posted by
cny-bikeman
I don't think it's a good idea to do anything but take the bike to a shop. In addition to knowledge you are lacking the tools to do any of the work needed. Some of the advice above is questionable, esp as regards throwing your cassette on a new wheel, as the cassette must be the problem.
If it truly is a cassette and not a freewheel than the freehub is the problem, not the cassette.
If this was a freewheel than I would agree, that is the problem since the pawl mechanism is inside the freewheel.