I lost handfuls of hair and had bald spots for months after I went off bc pills (yasmin). My hair looked really pitiful for a long time. It was completely depressing, so I understand how you are feeling.
A year after going off bc, I got preg, and hair started looking a little better, but after baby came, I lost some more hair.

Now, almost 2 years after baby, a lot of it has grown back. It is not as thick as it used to be by any means, but it does look a lot better than it did.

I used nioxin for a while, didn't seem to make any noticable difference for me.
Hugs to you. I know how bad you're feeling about it!