My difficulty comes from the last line. I apologize for the lack of a period on the last sentence there should be one there. I realize that {{JP:かきむしる}} means something like "to scratch off" and that {{JP:おさえる}} means something like "to seize/grab hold of." I know that the first verb is modifying the {{JP:よう}} but unless the reading "I grabbed the scratched off scab on my back" is correct (which is what I get from looking up the meaning of {{JP:よう}} ) then I'm stumped. Could anyone illuminate it for me please?

Here is some context: