Okay so we have one of these at home (we're not that flash, was given to us by a friend moving house!!) - its just like the ones you find at service stations etc. Is it safe to use? Am 34 weeks today. I know they say to see pregnancy trained professionals if you go for a massage, but is that just because you will be laying on your front? My back is killing me, someone please tell me I can sit in it for twenty minutes!!!