My oldest son (now 13) did not sleep the first 3 years of his life. and still to this day he is a night owl and still does not sleep. I slept when he slept. My work hours at that time where 4-9pm.
My story, like yours, slept great until about the 8 week mark(you know the time we go back to work and need sleep). Then he was fine when I was holding him, the minute I put him down, cring and screaming. His best sleep time was 4-9am. Really, I slept on the couch with him on top of me every night and every nap or he did not sleep.
He also started teething at 14 weeks and by the time he was 1, he had all but 4 teeth.
When he did stay in his bed and sleep (at 2-5), in the morning when he heard we were up, he would come find me, hold me and go back to sleep on top me for another 45-60 min. today still curls up next to me on the couch to watch TV, a snuggly guy.
With my 2nd son (4 years age gap) I got a full size bed in his room just so I could just sleep there with him if needed(work hours changed), and did 60% of my nights-why not? It is only a short time in their lives. And it was better then the couch or in my bed with another adult you are trying not to wake. I sleep- they sleep- dad sleeps. We did not as many sleep problems with #2 like we did with #1.
for son #3, I still have that full size bed. Where do I sleep? This one is a dad's boy, so dad sleeps in the bed with him. Not much now (he's 3 now), but they just love to be with us (children want to be with their mommies and daddies). And in time that lessens and they move out.
My Dr. said if my oldest son didn't sleep by 18 would talk. He just likes to stay up all night. He also did not and does not, eat much. He also was the bed wetter. He was always small compared to his class but now is starting to pass them in height.
Hopefully nothing serious is wrong with your baby. He may just miss you, want to be next to you.
Good luck