Mazda refuses to reverse

I have a 1995 Mazda Miata with a manual transmission. Lately it has been getting harder and harder to get the car into reverse, 1st, and 2nd gears, and this morning it was impossible for me to get the car into reverse. Do I need to replace the clutch? Is it something else? Any help will be greatly appreciated!

Can you put it in gear with the engine not running? If you are stepping on the clutch and it is not disengaging the transmission, you may be in need of a new one. It may also be in need of some fluid in the hydraulic system for the clutch, that is the clutch slave and master cylinders. Check the fluid reservoir first.