Thank you for writing to us.
With two negative pregnancy tests, changes of pregnancy are remote.
To confirm ( since you are not having regular periods ) go for a blood B HCG pregnancy test or a pelvic ultrasound.
Also, regarding the other symptoms, they are also not uncommonly seen with the Mirena IUD.
It could be possibly responsible for them.
Flagyl would not cause all these symptoms, particularly after stopping them.
If the gynecologist has cleared you of pelvic infection, then the possibility is the Mirena IUD, which is known for causing these side effects.
Please consult your health care provider regarding the same, and if they are really bothersome, consider removal.
Hope this helps.
Take care, and please feel free to ask for further clarifications.