HCG 0 but five positive tests?


Riddle me this:

My bff has an IUD in. After 4 kids. 3 of which were a little bit tricky to conceived (each took 6+ mo and lots of chemical miscarriages).

She felt nausea and tender breasts so she took five tests, all positive. Not faint, not blazing. But clear positives.

But her HCG blood work is 0.

What is happening???