I can't believe it!!!

My son is 3 weeks old exactly and he just rolled over from his belly to his back! I thought it was just a coincidence, but then he did it again within just a few minutes. Granted he is a big boy. He weighed 9 pounds 10 ounces and born on his due date. He also has amazing neck control, coos all the time, swats at toys, and recognizes when I enter a room. He eats 4 ounces every 3 hours too.... my daughter did not hit milestones this fast. I feel like I gave birth to a 3 month old!! Why can't he just stay little?