It is difficult to determine the type of side effects that are usual with your IUD because you did not mention the type of IUD that was placed.
I suspect by what you described that you may have had a Mirena IUD placed. If that is the case, you should expect this side effect. Having a lighter and possibly absent period was one of the deciding factors for me in having the Mirena placed. I was plagued with very heavy periods and did not want further children at the time. Uterine ablation seemed too permanent because there was a slight chance of wanting a 3rd child.
So, I opted for the Mirena and it has been the best thing ever. There are always potential side effects with any medication, device or medical procedure so education and weighing the risks vs benefits is suggested with anything.
If you do have a Mirena, I can tell you that most women experience a 90% reduction in their menstrual cycle and some women's cycle ceases all together. I would suggest visiting www.mirena-us.com/ for more information.
If you do not have a mirena, you should contact your healthcare provider. If you do have a mirena and are still unsure, doubtful or the side effects are unacceptable to you, you should also contact your healthcare provider.
I hope this helps.
Also, nausea and vomitting is NOT normal over a 2 month period. This warrants a call to the doctor. It may or may not be related but in any instance, is not something that is normal.