Weak & shaky all of a sudden

I was just sitting here and all of a sudden I got really shaky and when I stand up I feel my limbs getting really weak & I get dizzy and have to sit back down. I ate roughly an hour and a half ago, and my lunch hour is in abouf 15 minutes. I don't know what's going on & im worried I'll pass out. I can't call my doctor until after school, so I'm worried I won't make it until then. Ugh could it be a blood sugar problem? Or what? I'm 20+4 weeks