Pulsating or twitching tummy

I'm a first time mom, current 8+1 wks. Randomly throughout the day I feel like my lower abdomen is pulsating and it's quite strong. Anyone else feel the same? Is it normal? There's no pain when it happens but I have backache every night usually at my lower back/tailbone snd pelvic area.#firstbaby #1stimemom #pregnancy #advicepls