Acne and weight gain are not side effects of an intrauterine device (IUD). There could be some problem when it is inserted (damage to uterus, expulsion of the IUD, increase risk of future miscarriage, and pain). However, since you are using it for a while, you may not have to worry about these now.
The long-term side effects of IUD could be menstrual problems. Some women find that their periods become heavier, longer, or more painful. This may lead to anemia (due to bleeding) and its associated complications. There is a small risk of an infection of the uterus (pelvic infection). The chance of becoming pregnant is very small if you use an IUD (but not zero, no contraceptive can be 100% safe). However, if you do become pregnant in future, there is a higher than normal chance of having an ectopic pregnancy (that is pregnancy outside the uterus), but that does not mean that every women using IUD will have ectopic pregnancy if they become pregnant after using IUD.
It seems that you have moved to Canada from Pakistan and changes in your diet, environment and physical activity have most likely occurred. This could be at least partly responsible for these problems you are having.
Try to eat healthy (fruits and vegetables more than fats) and keep your face clean (perhaps limit use of cosmetics if you are using such things, wash frequently with water and mild soap and pat dry [not rub the face with towel], avoid using oils to prevent accumulation of grease on face, and do not pick/squeeze the acne).
As it seems that your problem is not as serious as it used to be in the past, you may consider seeing a dermatologist for your problem, and s/he may give you some creams or medications to use for your acne.
Hope this answers your questions.