I'm 15 weeks gestation and I'm still sleeping on my stomach - I've always slept this way (even as a baby, apparently as soon as I could roll myself over, it's what I did!). Even if I start off trying to sleep on my side, as soon as I'm drowsy I roll over onto my tummy. So far it's not causing any problems I don't think - I do get pins and needle sensations in my thighs but I have that during the day too, so I'm not sure that it's caused by my sleeping position but probably the baby pressing on nerves/arteries.
I realise in my 3rd trimester I'll need to sleep on my side for safety - I'll have to wedge myself in with pillows and just hope I manage to get some sleep! But has anybody else slept on their stomach during the 2nd trimester until they got too big? Did it cause you/the baby any issues?