Am I Pregnant? What's Going On?!

Molly • My name is Molly. My fiance and i are trying for baby numbet one. I was diagnosed with PCOS when i was 16. I'm currently taking metformin to (hopefully) help me get pregnant.
Okay I took this test a few days ago. It appears to be positive. I took another pregnancy test today and it was negative?!?? 
What does this mean? Is there any possibility I'm pregnant?