Someone please help. I can't handle this.

Hello.I can't handle all the stuff that has been happening recently. It's too much. Please, someone help me.

My name is Grace. I am 13 years old, a touch bipolar, and possibly have an inferiority complex depression.
It all started two years ago. The depression, I mean.
In the summer of my 6th grade year, my grandmother, my last grandparent, died.
A few months later, one of my cats disappeared. And another cat a few months later vanished as well. Both I had for as long as I could remember.
6 months later, a cat who we had since he was a kitten, and who was older then me, had to be put down.
And another passed away a few weeks after that.
Then, a week ago, we found out that my cousin was dying. She had a terminal disease, and all the doctors said she wouldn't live past twenty. She's 29, and now she's dying. My mother flew out to Virginia to see her.
While she was gone, my dog, who we have also had my entire life, finally snapped, and attacked my dad. The dog had to be put down.
Without my mother to talk to, I snapped. Broke down sobbing in the middle of class (twice) two days ago.
Now my mother is back, but I don't feel better. I have no energy, and I just want to curl into a ball and sleep, because you don't have to think when you sleep. I feel like I'm being crushed.
I used to be an insomniac, but I thought I had gotten rid of it. Now I can't sleep again.
I've always tried to compare myself to my sister, but she's brilliant, beautiful, and talented in so many ways. And she's not exactly nice to me. Not mean, usually, but she never supports me, and insults me all the time. Hence the inferiority complex.

Also, I hate pity. I hate people treating me like I'm fragile and broken. That's why I don't tell my friends my problems. That, and they have enough problems. They don't need mine. My job is to listen to their problems, not to list mine. I also hate self-pity, and so I don't let myself confront my issues and, consequently, feel bad myself.

This is starting to affect my brain and my actions. I can't think, and I've developed several nervous tics. I've made more typos on this little entry then I can count. I also twitch.
I believe the stress of events combined with the pressure to do well in school, and the frustration at the immaturity and stupidity of those around me is driving me to depression. I don't think I'l go as far as suicide (although the thought has occurred to me), but I definitely need help.

I apologize for any errors in this comment.
Thank you.