Still waiting

Maggie
Super annoying, I went for an ultrasound April 1- a gestational sac was seen but appeared empty. A follow up scan nine days later showed a slightly larger sac that also appeared empty. The doctor then ordered blood tests, four in a week... And the hcg level keeps rising. My doctor is confused and has said it may be an etopic issue... 
Anyone else had anything similar? I go back on Friday for anther ultrasound.