Its probably baby and its either the head or butt. Im 33 weeks and my baby is now head down but I can feel her butt all the time and she moves all over but prefers my right side
Its a little hard and it stays in that spot until I get up or turn on my side but its not always on the same side
Probably baby just shifting inside. You'll notice as you get bigger sometimes they shift completely ton one side and your whole stomach is lopsided