Thanks for your query.
As you had the faintest of positive lines, you do have to strongly consider the possbility of pregnancy
The faintness could be indicative of a very early pregnancy , or a failing pregnancy, or an ectopic pregnancy.
You are going for a scan tomorrow which would be confirmatory.
The symptoms you have would be ascribed to a pregnancy if it is present.
After removal of a non hormonal
IUD alos, the body does take some months for re adjustment as the coil alters the endometrium and the internal milieu of the uterus
It is not wise to comment or indulge in guesswork till we have the result of your scan in hand.