I agree that you may be putting him down too early. I was very lucky with my kids they slept well and only cried when something was wrong. What kind of a cry is it? Tired? Pain? Hunger? Will he let you hold him? How are his bowel movements? Could his acid reflux be acting up again? Suffering from that myself I'm here to tell you there are times I would like to scream too.

I had my neice and nephew for a while, they eat had a stage where they'd cry for a period of time (about a month as I recall) for no apparent reason. My mother in law called it growing pains. We just made sure that we took them outside to get fresh air, then had a nice bath and story time. Whether this was effective or they just out grew it I don't know. When they were crying the only thing we could do was rock them and talk to them in a soothing voice.

As a side note, when my twins were a bit older than Jeremy is now (about 18 months) my parents got one of my other kids a trampoline for their birthday. The twins loved it SO much they didn't want to come off of it. They were like energizer bunnies. I thought "oh, ok, I'll just let them wear themselves out and they'll go to sleep when they're tired." That point never happened. That summer they jumped on that stupid thing every day rain or shine for 12 - 14 hours a day. Continued doing this until about 3 years ago (they're now about to be 16).

The point I'm trying to make is that as long as there is a stimulus, he's not going to let himself relax. Is the TV off? Room Dark? Make the environment such that the only thing to do is sleep.