what to do about side effects?

Before becoming sexually active I was on the pill to steady my period cycle. But I found I was becoming nauseous the first day of taking my birth control after my period. I went back to the doctor and got a lower prescription and it worked great! But now that I have become sexually active I should be on a higher dosage of birth control, I don't want to have to side effects of a higher dosage, so I have considered an IUD, but I want to know side effects and how well it works before going forward with it. Thanks in advance