Its still early to feel the baby, but by the time you are 16 weeks along or so, sometimes that 'hardness' you feel is the baby's back against your stomach wall. If they are facing "in" and presenting their back to your belly button, you can kinda feel it... when they face the other way, tummy tends to be softer.
Your placenta might also be in the front and that's what you may be running into.