"Has found out thy bed of crimson joy"-Whom does the word 'thy' refer to? What did he find and when? What does the expression 'crimson joy' suggest?

This line is taken from William Blake's famous poem "The Sick Rose". Here the word 'thy' refers to the rose.

       The invisible worm has found the bed of rose. The bed is of deep red colour. This bed is thus nothing but the deep red coloured petals of the rose. He found it on a stormy night.

      The expression 'crimson joy' refers to lustful passion. It suggests sexual pleasure. It has been used to describe the lovers' bed. From another standpoint, the phrase 'crimson joy' suggests ensuring beauty. While the crimson colour soothes the eye of tge viewer, the perception of the expression of joy satisfies the heart of an onlooker. There it also stands for the repressed sexuality of the rose.