고 어쩌다

what am I supposed to do?

어쩌다 is a contraction of 'how to do', and it survives mainly in a handful of fixed shapes, all of which appear here: 어쩌지 / 어쩌죠 (what do I do?), 어쩌라고 (so what do you want from me? — sharp and dismissive), 어쩔 수 없다 (nothing can be done about it), and 어쩌고, a stand-in for the rest of what someone said, like 'blah blah'.

Register: 어쩌라고 is rude; 어쩌지 is ordinary worry