Early periods

Ireland

My cycles are getting weird, period used to come on the 27th (give or take a couple days) like clockwork, but the past two months it came early on the 19th which isn't awfully early but it's still early, and this month it came on the 10th which is very early. I don't have health insurance which is why I'm not asking a doctor, but it's kinda concerning to me. I just want to know if anything could be causing it or is it normal? My grandma said it might be stress but I've been very not stressed as of late.