He might be used to you holding him when he sleeps and maybe he just needs to wean onto the bed. 

Melissa.

Aww.. your baby hasn't even been out of the womb a fraction of the time he was snuggled safe and sound right next to you.  If you have a wonderful family bed - it's natural, it's normal, and it's the way babes were meant to sleep - I'll bet you and baby will get so much more sleep!  SIDS is ridiculously rare - you have a higher chance of hurting babe in an automobile accident than you do of his succombing to this very rare and unpreventable syndrome - that you really needn't worry about it.  All four of mine were tummy sleepers and slept fabulously, but it's a choice I made - by making that choice, I didn't worry about flat heads, gas/reflux, frequent waking, jerk reflex, or any other problems.  It's a personal decision.  But the decision to have a family bed with all four is the best one we ever made!!

SANDRA
Co-sleeping, non-vaccinating, free-ranging, gentle disciplining, attached mama to four babes, Brett (16), Justus (11), Autumn (4), and Ayla (1)

Never put him on his belly. Do you swaddle him, because that makes a big difference. Babies are use to being tucked tightly in your belly. So you need to tuck him tightly with the blanket. Also try feeding him right before bed and a fresh diaper.I some times use a wedge and put my son on his side. He gets gassy and this makes it easier on his tummy. That also might be an issue. Does he draw his legs to his stomach when he cries. That could mean gas. Which make sure with your doctor but there are drops that are life savers to say the least. Make sure he is warm when you put him down, but don't let him over heat as this is also a cause of S.I.D.S. When all else frails some times children get spoiled from holding them all the time. We are all guilty of it especially with our first baby. So lay him the crib and let him cry it out. He will be fine. If you pick him up every time he cries he will expect it. Trust me I have to boys and every now and then I realize I have been giving in to their every whim. Good Luck. I hope that helps you. By the way if none of these things work I would see a doctor just to be sure it is nothing serious. I am sure he is fine but safe than sorry.

Even Dr. Sears' website says if baby is more comfortable sleeping on his tummy, then so be it.

Tummy sleeping does NOT "cause" SIDS - you will not find that anywhere.  And they still can't prove it's reduced infant deaths; for example:

In 1991 10 babies die of no apparent cause in their cribs; all called SIDS on the death certificates
In 2009, 10 babies die of no apparent cause in their cribs; autopsies performed, 2 are found to have heart defects, two with brain/spinal cord problems, and one with lung problems; five are still mysteries, ala SIDS. 

VIOLA - a 50% reduction in infant deaths since the Back To Sleep campaign started.

It's false statistics - infant mortality hasn't changed (actually, I believe in 2005 it increased), it's just that deaths are being reclassified now that autopsies are being performed.

Tummy sleeping is not a death sentence.  To allude to that just adds to the scaremongering every new mom goes through with websites like this and internet chat rooms and fearmongering media.

I had the same problem with my son! I thought that the mattress had to be the problem and after trading it in 4 times I realized it wasn't the mattress at all! I tried warm baths before bed and that worked for maybe 45 minutes and he would be screaming like he was laying on a bed of nails so I took him to the first pediatrician that I would trust with my son and he gave me the best advice ever! I would take and give him his bath or rub him with lavender baby lotion! I would take the blanket and lay on one side of it then his dad did the same! I took a old wind up clocks that ticked and I wrapped it in a sheet and put it above his head! I swear that Dr. tucker is a genius if he was fussy with dads smell it sure will when i flipped it and if that still didn't work you take that blanket stick it in the drier on high for 5 to 10 minutes Take and swaddle the baby make sure that the clock is ticking and with in 5 days of doing that my son slept threw the night except when he wanted his 2 AM feeding and then right back to sleep he went! I hope that this helps good luck and god speed!! JAMIE J ANDERSON Riverdale UT