Irregular Sleeping and Eating

My seven week old son did not nap at all yesterday. He is not normally a good napper to begin with but usually I can get him to take at least two naps a day. He finally went down last night around 9 pm and for the first time since we brought him home he slept for three hours without waking. He woke and ate two ounces of expressed breast milk and went right back to sleep.

Now it seems all he wants to do today is sleep and is uninterested in eating. Whereas previously he wanted to eat ever hour and a half. Anyone else experiencing this? Should I call our pedi? Thanks!