There's something wrong with my menstrual cycle....?

Im 17 and this past year there has been alot of changes with my body....my periods use to be regular but since like december they have either been late or unusually lite.... I googled it and it said I could be infertile...is this true? Also my boyfriend and I have sex without protection and he has admitted to me that he has made multiple mistakes in me....and ive never gotten pregnant...so now im kinda worried..because I want to have kids in the future..please help.....