I know with my little guy I had to rock him and he had to be asleep for about 10 minutes before I could put him down oh so carefully. That went on until sometime around 6 or 7 months and suddenly one day he was able to put himself to sleep. I figured it out by accident one night when I really had to use the potty so I set him down and when I came back he was asleep. Now at 10 months he needs rocked again some days.
I don't know if you use one or not but the pacifier has been helpful to us. He didn't sleep with one much until about 8 or 9 months when we started transitioning out of co-sleeping and he was teething. He finds it very comforting and it helps him settle.
Everything is a stage and the stages seem to cycle. Enjoy those snuggles!