Am I going to go blind? Is a cataract blocking my vision; sometimes I see ok, sometimes not good?

Blind? Not sure about going blind! Anything is possible from the symptoms you are describing. Most likely the condition causing your fluctuating vision is not cataracts. The cataracts do not cause the vision to fluctuate. They can cause different degrees of symptoms depending on the environment, ie. Bright light, night time, sun light, reading.
See a doctor. Cataracts generally develop gradually and slowly with rare exception. They may be more noticeable during certain lighting conditions. If your vision is deteriorating, see an eye doctor to get a proper diagnosis and rule out other conditions.