It seems like you're having a terrible time right now, and that completely sucks. One thing to keep in mind, though, is that just because everything isn't 100% cured by the thyroidectomy it doesn't mean that it hasn't helped or won't help in the future. Mood disorders are complicated, and it's unlikely that they're ever caused by one thing alone. So even though you might still have symptoms after the thyroidectomy, it's very likely that the symptoms will be less severe/less frequent.

Also, I understand what you mean about feeling worthless. But one thing to keep in mind is that no human is truly worthless (I genuinely believe that), and that includes you. Everyone has worth because they are unique and offer something that no one else can just by being themselves. Cognitive therapy helped me a lot with my thoughts like this. Feeling Good: The New Mood Therapy is a great book about cognitive therapy, and you can get it for pretty cheap on Amazon.

I also understand that you're not acting in a certain way to get attention, and it's a terrible feeling when other people think you are "acting out" for attention. Just hang in there and it WILL get better, even if it doesn't feel like it at the moment. It always gets better. Even the worst mood episode doesn't last forever. Just keep telling yourself that. Also, go easy on yourself. It's often so easy for us to have compassion for other people but not for ourselves. Be compassionate to yourself. Be kind to yourself. You deserve it.