Rhythmic pulses in belly

Hi everyone, I am 35w5d into my pregnancy and I recently started feeling rhythmic pulses in my belly. These pulses are stronger when I lie down, stay for around 15 mins and then stop. This happens a lot of times during the day. This is definitely not baby's movement nor the heartbeat. I am not sure if this is normal since I read a lot of scary stuff online for pulses in belly. My appointment is next week, so I am not sure if I should consult doctor now or just wait until next week. Anyone has any idea about it?