Please help baby wants to sleep on tummy only?

You can try on of those newborn postioners. My son was the same way. I let him sleep like that during the day and just watched. I figured since he never ended up with his face in the matress i let him sleep like that at night. When they get to be 5 or so months they figure out when they cant breath and will move theyre head. You can also try to just put his car seat in the crib, strap him in and rock him to sleep. Or the bouncer, or just leave him in a swing. If you dont have any, you can roll blankets up, starting with a small on and up to a larger one (baby blankets) to make a rap. Then lay a folded blanket over the small ramp and place your baby on his back on the ramp after he has fallen asleep. He could have acid refluxe, causing him pain, or just stomach pains.