Soo by the math I should be 8 weeks pregnant today. I’ve been having a lot of cramping and back pain. So I found a doc that would check me out b4 12 weeks. Of course the pee stick came back positive. But when she did the ultrasound there was nothing. Not even a yoke sac. I recently had a miscarriage so I’m super upset about this. She did take blood and depending on my levels I come back ina week or two. Has this ever happened? Should I be more concerned