Mazda Clutch Mystery

I have a 1993 Mazda Protege DX, and I cannot changes gears while car running. First, my dash brake warning light came on. I recently learned that my brake fluid reservoir is also my clutch fluid reservoir. The brakes continued working fine, but one night it became really hard to shift gears and by the next day it stopped shifting altogether. Since then I've refilled my fluid and the dash brake warning light is off, but I still cannot shift and when I try I smell burning - that just started. In hindsight, I recall my rpm's going higher than usual while shifting/accelerating and 1st gear was sticky I've googled info on this and there are just too many possibilities. So far, the best theory seems to be possible air in clutch from when the fluid ran low/out. PLEASE HELP with any experience or advice!!