I know you are only supposed to sleep on you right and not tummy or back but when does this start from? I am 15 week and find it really hard getting comfortable. Surly the back thing is when the baby is bigger and it is to do with the weight putting pressure in a vein or artery so presumably this is only later on in pregnancy? And sleeping on the front is that only to do with being comfortable or will you actually squash the baby??