I also felt this but around 15 wks. I also thought it could be baby but it felt quite strange almost tender to the touch..I think it could've been contractions since the bulge didn't disappear when I stroked it, whereas now that I'm feeling baby a little more, when I stroke the area, there is movement ..almost like baby going in hiding or changing position/direction. Having said this, after getting these 'contractions', it seems my belly is firmer and my uterus seems higher (like towards my belly button). These are just my thoughts, I dont know if this is true.
It's mainly in the morning but today it was in the afternoon..
Its your baby is itb in the morning?
Im also 17 weeks pregnant :-)