Is something wrong?

My son is 3 weeks old. When we brought him home from the hospital he would sleep for 2-4 hours at a time and then wake up to feed. For the past week he started waking up way more often, like he would sleep for 30 minutes to an hour and wake up crying. Before he would slowly wake up and stretch, grunt, all that stuff but now he pretty much starts crying right away and I pick him up and he falls back asleep. So he doesn't wake up because he's hungry and I don't know what it can be. Is something bothering him?! Please help!