so when im in 2-5th gear and i step hard on the gas, my rpm shoots up about 2000, then back to normal. so i figured the clutch needed to be replaced. but if i do it again right after, it doesnt do it, it just slowly accelerates. and i took it to a mechanic and he said the clutch seemed good. any thoughts?

What you have described is a slipping clutch disc. Find a road with a hill and get to 45mph up hill mash gas in 5th gear if Tach shoots up then clutch slipping