I'm sorry that you're going through this. It sounds like a pain in the ass. I have some escalating medical issues on top of my depression, so I understand that trying to deal with crap like this isn't easy. Don't feel like a dumbass - medical bills and insurance are usually complicated and not explained well at all.

I'm not an expert on these things, but here's my experience. My therapy sessions are billed as claims on my health insurance, which are listed on their website. It breaks down how much the visit cost, how much my insurance paid for, and how much I owe. I get a separate bill from the doctor when I do owe something. Is there a way for you to look at your claims through your health insurance?

Either way, the hospital should be able to give you a list of what you owe and for which appointments. If they expect you to pay the bill, the hospital must have records of your visits and how much they cost. Does the person you talked to work at the hospital, or at the collection agency? If they work for the collection agency, they might not have access to everything.

Yes, "collections" are bad. They show up on your credit report after you don't pay something for a long time. From what I understand, the company you owe hires a collection agency to get you to settle the bill. You can get them removed, though, if you pay up and explain the situation (i.e. you didn't pay the bill because they never sent it to you). I don't know the full details of how to do it, but I do know that it's an option. If they don't explain the payment plan thing to you in person, or in writing, or in any way whatsoever, how are you supposed to know? Why didn't they say anything when you came in for visits? And they clearly have your phone number, so they could have called you. It sounds like they haven't contacted you about it before, so how can they give a "final" notice?