Can he roll over? I'm assuming he can since he can crawl. He may have gas. My son did, and believe it or not, the doctor suggested I put him to bed on his tummy. I found it took about five minutes for him to cry it out, and it was really a cry to express his discomfort, and to settle himself to sleep.
I had walked the floor with him for well over a month before I resolved this, but all he wanted was to be left alone in a dark room so he could sleep. BTW, I called my mom, and she said I was the same way when I was little!
He may simply be too tired, too, and he just needs no stimulation, just darkness. Many kids and adults sleep better in complete darkness and isolation.
Just an idea. Good luck!