Hi there guys, hope you can help me on this

Well basically was driving down the motorway in 5th and suddenly theres a grinding noise that appears, and basicallt the more i pressed the accelerator the louder the noise got, i then put the car into 4th gear and was gone and luckily i got back, but the petrol was drinking like mad lol

does anyone know of this?
hope it isnt the gearbox? , cud it be the clutch by any chance???????