I just passed out for the first time and I'm tripping out?

So I was cutting a pen with some little blade and it was kinda hard to cut so I applied mor force but slipped and cut my thumb really bad.... Then blood rushed out and started to drip so I get to the restroom and more blood was rushing out and the next thing I know my head gets super light headed and I pass out I wake up 3 sec or so later and I try to get up but I'm twitching as I'm getting up so it was prettty awkard and soon after my brother rushes in and helps me up but my question is why did I faint and why did I twitch when I was trying to get up ??