i couldn't do nothing,but thinking of you.------what does th

i couldn't do nothing,but thinking of you.------what does that mean?
i couldn't do nothing,but thinking of you.
------
what does that mean?
是不是等於i couldn't do anything,but thinking of you?
有没有再详细一点的？关於这些句型的？是不是所有句子的否定加否定就都等於肯定？