Is my gerbil dying?!?

My gerbil sandy hasn't been himself lately, he's not eating or drinking he's not playing and all he wants to do is sleep. He NEVER used to let me pick him up or stroke him or he would CHOMP really hard and draw blood but now he does without biting. He's about 2 years old. When i put him on the floor he starts shaking. If you listen closely in the video he makes this noise that sounds like he's eating, but he isn't eating at all, not even treats. He isn't as fast anymore and he had crust on his eyes the other week. Yesterday he was happy and he would run about but today it's the opposite. He is really skinny compared to yesterday. I remember him finding a really old and stale cheerio and eating some. Could it be that or is he dying?? :'(he seemed fine after the crust in The eye, warm water helped open them because the crust glued his eyes shut.