I had depression that nearly killed me. VERY nearly.
How many people did I treat like your ex treated you?
NONE! Not one, not a single one.
I will bet that your childhood/upbringing taught you that you were not worth kindness/love and this guy was drawn to it.
i just feel like i lost "me" throughout all this and feel responsible
'Me' was stolen/erased and told she wasn't valued, she was taught to please others rather than love herself. Probably before this guy rocked up, but now you know that Me was AWOL, it's time to invest ALL your energy into finding who she is and what makes her happy and brings her joy.
I had this, a life time of being told I wasn't good enough leading to an abusive relationship where I had no power or ability to stand up and say No. When he left, I found the way to say no. My family HATED it, (they'd tried to keep my very clearly abusive relationship going somehow, it suited them to have me curtailed) the sense of strength I got, the ability to call my own shots, to see that actually i COULD manage my life very successfully actually thank you very much was really powerful.
the next step was to realise that as empowering it is to learn that you have the ability to say NO, it's important not to say NO to yourself! It's important to challenge yourself to be a little bit braver and do the things that you were always told you shouldn't/couldn't if there was no really good reason why you shouldn't.
I don't recognise the person I was back then, frightened of everyone and everything. I was a lot like you, I know that you won't always feel like this and I know how much great potential you have in you, so please just trust us and stretch those wings so you can fly :D
i was a nervous wreck at the end because i didnt know where i stood with him
Spaghetti head - that's what they do. they mess up your thoughts and life to keep you busy, to keep you so distracted generally that you won't realise what they are doing/how crap human beings they are.
They do all of this from weakness not strength. They are deeply insecure and know they can't compete with normal human beings on the same level playing field, so they destroy all those they can around them so THEY look and feel powerful.
if you take only one thing from any of this, take this:
It was NOT you. there is nothing you did that made this happen.
YOU are good enough as you are, if people don't like that, then they don't get to have you in their lives.