For the first couple of months it may not be as your body adjusts to it. There may be some spotting, and like you said you may not get your period at all. For some people it will then be regular. For others it won’t. Personally, I’m at about the 6-month mark and I’ve found that I get my period every other month at this point.
According to this very helpful section of Mirena’s website, 1 in 5 people who get the hormonal IUD will stop getting their period altogether. For others, their period will go back to what is normal for them. To sum it all up… it is impossible to say exactly how your body will react to the hormonal IUD, but there is a good chance your period will be more consistent or stop coming. Your best bet is to discuss with your doctor how it may work with your body. Since they have a good idea of your overall medical history they may be able to direct you to the best answer to this question.