Which is grammatically correct?
i listened but heard nothingi listened, but heard nothingi listened; but heard nothing
The second one actually. There should be a pause between the two to indicate an intake of breath. It also depends on how you want it read, if you want it to continue in a stream very quickly or if you want the pause.
the first one
None of them the I is supposed to be capitalized
it is i listened but heard nothing......bye
Second is correct.