Waalaikumsalam sis! Mmg ada a few of us yang pernah rasa macam tu, sometimes it's just gas, bloating, or muscle twitches yang terasa macam pergerakan, especially kalau perut anxious atau hormones tengah naik turun. Tapi sebab test negatif, I'd really suggest check dengan doctor je to rule out anything else, biar you dapat peace of mind, maybe ada urinary tract issue or something lain yang perlu attention. Don't worry, usually benda macam ni boleh solve dengan simple check-up!