Poor sleeping patterns are common in many babies with colic or reflux. Getting your baby to sleep for longer periods during the day or night can make a huge difference, as colicky babies need sleep.
As a general rule, colicky babies sleep best on their stomachs on their mom. A combination of pressure and warmth often get gas to release and move along.
Sleeping on their left side may help burps to escape. It is worth trying this for a few days to see if they are more comfortable. You probably wont be around to hear the burp come out but they may sleep for longer or be more comfortable.
Babies that are suffering with reflux should probably sleep on their sides to minimise the risk of choking. You might raise the head of their cot with a couple of bricks or a wedge under the mattress.
As a general rule of thumb .... let the baby decide what their best position is. You will know because they sleep longer. Just make sure that a blanket cannot cause re-breathing (breathing in their own air is the chief reason for concern about sleeping on stomach).
Watch Dr. Sears' Top Baby Sleep Tips to find out more