Growth spurt?

My LO is almost 12 weeks old. Yesterday and today he has slept all day long. He slept between 8 to 12 hours and has only gotten up to eat maybe 4 times since yesterday morning. When he does wake up he isn't fussy or crying like he needs the food right now or anything. I'm just wondering what to do about his feedings. I don't want him to get sick from not eating. He is also teething. Thank you