Worried after first scan! Need reassurance!

I went for a scan today as iv been having bad pains I'm bottom of my tummy sometimes period like sometimes sharp, they could see a sack but nothing in it so I had a blood test to see hormone levels and have to go back on Monday to see if they have gone up and also another scan in a week. They said it could either be a phantom pregnancy, or just to early to see anything has anyone else been through this cause I'm getting really upset and worried! Thank you