Achey spot


I am 29 weeks, and for the last few weeks I’ve had a spot on my belly that constantly aches. It’s not a visible spot. In fact, when I inspect it I can’t see anything there at all. But it feels like the same sensation as someone poking a bruise. But even without me touching it. It usually hurts more later in the day, but the feeling is becoming more consistent. Any ideas what this could be?