should i be mad?

That's just weird. I have a sister, and I've had sex with lots of girls. And by lots, I mean way more than I reasonably should have. And believe me, I don't think of any of any girl who had sex with me the way I think of my sister. Because I haven't had sex with my sister, in fact I don't even want to. Because that's just really really wrong.

Of course this guy doesn't understand why you're mad. He thinks of you as a sister, even though he nailed you just last week. Basically, this guy thinks nailing his sister is some sort of normal thing.

Trust me, you don't want a long term relationship with a guy who thinks like that. Not even for a little while, because he's just too f**ked up. Don't be mad about it, be happy. You just dodged a very huge and very-very weird bullet.

Okay, so you lost your virginity to a guy with a severe mental illness. No big deal, lots of people have mental health issues and lead (mostly) totally normal lives. It's not like you knew he was nuts or anything, so you can't be blamed for what happened.

I'd be furious and heart broken at the same time.
Sadly from your description, your boy 'friend' sounds as though he was only after sex.
Yes he may of enjoyed but didn't think about the future.

Have words with him and explain how it's not right or fair how someone can go from a couple to friends within a day.

You sound like you can do better.

Learn from your mistakes.

Good luck.

Seems like a player....he just used u fr sex....so gross that he thinks of u as a sister ?
Get away girl...run !