Sleeping dilemma

When Jacob was born, Ryan and I had a very hard time getting Jacob to fall asleep. We would sit on the couch and rock him, swaddle him, rock him in his room, rock him on his bed, give him his pacifier, etc. and if we were lucky, he would fall asleep after an hour or so, when Ryan and I were just about in tears with frustration. Then, Ryan and I got smart - we started putting him in his crib at the first sign of sleepiness - ear tug, eye rub, or a yawn. Jacob would fall asleep on his own and we were super ecstatic, to say the least!

For a while now, we've had a routine of giving him his dinner, Daddy gives Jacob a bath, then Jacob gets a little milk to top him off, and then we put the boy down for the night around 8:30 pm. This gives Ryan and me time to talk or do stuff around the house, then go to bed ourselves. However, the last two nights have been a little different. He'll fall asleep as usual, then after an hour will wake up screaming! The first night we tried rocking him back to sleep, but he just seemed completely awake; so after an hour of trying to get him back to sleep, I just brought him out to the living room. What did he do then? Played. Like a little energizer bunny! After 30 minutes, he decided he was tired and totally conked out when I out him in his crib.

Last night, the same thing happened. He woke up after an hour of sleep, played with Ryan for an hour, then peacefully drifted off into sleep.

What's going on? I really don't like this trend, yet we aren't sure what to do about it. I really hope this doesn't continue. Just when I think we've got it all figured out, Jacob changes things up to throw us for a loop. Ugh.