my advice would be just before he falls asleep lay him in his bed and let him fall asleep by himself, my 15 week old loves to be rocked but then i realised that he was relying on it to fall asleep so now i lay him in his bed and walk out the room and go back in 5 mins to check on him and then leave again then check on him, he needs to learn to self sooth.. good luck
We went through a similar phase a few weeks ago with our little guy. What we did was lay him in his crib and "pretend" to be laying down with him by leaning over the railing with one arm along his body and that hand on his head. Then with our other hand we would lightly rub/pat his tummy and "shh" and/or sing to him. He would cry/fuss a few minutes and then fall asleep.
have you tried to swaddle him, ive heard that this technique was a life saver with some moms when they had the same issue...
i swaddled my dd bcz when i put her down she would swing her arms wake up adn start crying. I swaddled her, let her fuss for a little with me nearby (so she will be comfortable knowing i didn't leave her) and she would be out for hours!