IUD- unprotected sex- non fertile- no period! HELP

So I have an IUD for about 5 months now, and they said when I got it in about a year I won't get periods at all. My boyfriend and I have unprotected sex all the time, and yes he comes inside of me. When I was little I was told I couldn't have kids even if I wanted to but I still got the IUD. I haven't gotten my period yet and it's going on 2 months, but I spotted twice. Very little, but still. And I did get small cramps/ tummy ache. Should I be worried???