7 wk 2 days

Had a ultrasound at 5wk 3d as I had some spotting! Was told they could see the baby but a flickering heart beat so they want to check again in 10 days! Went for ultrasound today and they could see the yolk but not the baby, has this happen to anyone? Going back in 1 week for another ultrasound! I'm over weight and due to the position of the womb I think they struggled with the 1st u/s too! Don't know what to think.... have I lost my baby or could there still be chance it's there somewhere!!!! So confused and upset but trying to stay positive!