yes the clutch is finished,
what you are describing is known as clutch slip...
so basically you need a new one.
I have just changed mine and replaced the slave cylinder at the same time as they are (i believe) prone to wear, and mine was leaking, i think most people will say to change this at same time as clutch... it saves you having to go back under there again anyway.
clutches are not that expensive nor is the slave cylinder, but you MUST make sure you attach the prop and the flywheel as they were because the whole thing is balanced, including i am led to believe the nuts and bolts!