I Feel Something Moving In My Stomach It Started Yesterday

I Feel Something Moving In My Stomach It Started Yesterday When I Had Sex With My Boyfriend My Period Havent Come On Since The End Of September But It Came On Like A Week Ago For Like 4 Days I A On Implanon "Birth Control" , I Have Pregnancy Symptoms Like Nausea, Dizziness, Heavy Breast, Mood Swings, Cravings, Something Moving In My Stomach, Little Lower Abdomn Cramps, Lower Back Pain "Not A Major Pain But Pain" But I Took 3 Home Pregnancy Test And They Were Negative, Can U Tell Me What U Think It Is