“Has found out thy bed Of crimson joy.” – Whom does the word refer to? What did he find and when? does the expression ‘crimson joy’ suggest?

In William Blake’s ‘The Sick Rose’, ‘thy’ refers to the rose.

The invisible worm found out the rose’s bed of ‘crimson joy’ on a stormy night. It is eager to gratify the repressed passion of the rose secretly. This is corrupt. So it is the evil desire that destroys the innocence of the rose.
The expression ‘crimson joy’ refers to lustful passion. It suggests sexual pleasure. It has been
iced to describe the lovers’ bed. It stands for the repressed sexuality of the rose. It is allurin worm. The rose, therefore, attracts the worm to be damned eternally. As , rose is sick with shame.