Based on the information you have your IUD removed and found the dark area in the right side of uterus
, having pain since last 3 months and had spotting of blood was noticed, you do have the positive history for the infection with IUD.
It does seem like an penetration injury
due to the IUD, which needs to be evaluated further, for which a visual conformation is needed rather then ultrasound
as its will not be as effective as the naked eye examination.
1) consult nearby OBGYN
as you will need a vaginal examination (for visual check up)
2) In case of fever
please visit emergency services as it will be a clue for underlying infection, and for treating it with antibiotic is necessary.
3) Please avoid sexual activity till it gets checked.
Hope it helps.