Sounds like you're either loosing your clutch or 1st gear is shot ..... Try this, may narrow it down, pull your emergency brake, put the car in 1st gear, ease out on the clutch and give it a slight bit of gas. Does the car attempt to lunge forward ??? Or do you just hear the grinding noise ?

In either case, clutch or tranny, sorry to say it doesn't sound good !!!
I wouldn't be driving this thing if I were you !