Lara,

a great catch that OP already gave in to blackmail, paving the way to more blackmail. I am not sure I agree with you on guilt, however: the way I read the OP, OP is taking antidepressants and has trouble sleeping because she is feeling apprehensive, at the end of her rope, anxious, helpless, and hopeless. I did not see any mention of guilt (and I am glad I did not, because the situation is already a mess and OP's feeling guilty would make it yet messier while adding no value).

I might be wrong in my reading, but my impression is that OP is a woman who is panicking and while panicking, she is making dangerous choices, such as giving in to blackmail more and more, and then feels that she is in a downward spiral (which is true).