While this is fine as someone who has slept on their tummy since birth I would Highly reccomend trying to change it - more so because of the problems it could cause later on. I find it way more comfortable (i even sleep on the lounge on my tummy) but I have suffered hugely with back and neck problems. I have had to have heaps of physio because of how out of alignment things are now.

Both my girls find it more comfy too - but i'm trying to get them out of the habit so they don't have the same probelms.