how do i become less socially awkward in middle school?

I apologize for the long story, but please just hear me out. I'm desperate and feel like no one understands me.

I've always been a shy person. It's in my genes. My grandma is shy, my great-aunt, and my dad. I always feel like someones always staring at me watching my every move waiting for me to do something stupid so they can tell the whole class and start laughing at me. Not a lot of people really know my name, even when I've been in some of their classes in previous years. My math teacher can't even get my name right! I have friends but I just wish that people would know who I am, instead of the silent kid in the back of class. I sometimes go whole classes without saying a word, even when I know the answer. I'm afraid it will be wrong and people will start laughing.

I was recently depressed back in 7th grade because I thought no one really cared about me or even acknowledged my existence. I was thinking about killing myself or running away. I never told anyone that except my best friend, who ended up saving my life that day. I'm over these feelings but I still feel them every now and then. And cry evertime I think about what happened.

I told my best friend about my issues with my awkwardness and she tries inviting me to parties and to hang out with her friends in a group. I'm fine when it's just me and her but when her popular friends from school come I just shut down and back out of it, becoming the loner once again.

Today in one of my classes we were supposed to do partner work with JUST 2 people only.

There was an odd number of students in the class. I felt extremely embarrassed when it was my turn to present and I had to go in front of class and tell the sub that I didn't have a partner. She wasn't very happy... -_-'

I spend my weekends inside on the computer nearly all day. I really dont have anything to do or look forward to so I sometimes sleep-in till noon and play flash games all day and night. I'm not in any clubs because even the nerdy hackers make fun of me. I don't go to school dances (even when my best friend bribes me to go). I haven't tried out for sports because I'm always picked last and no one ever passes to me. I have EXTREME anxiety (in line for a roller coaster my best friend had to hold my hands behind my back and I almost threw up in line. Even the elementary schooler was making fun of me) Nothing seems to work... I feel hopeless like I'm destined to be forever alone.

Please someone help me... I'll try anything to become more sociable... Please