Periods on paragard

Olivia
 I'm a twenty year old college student who's tried both the pill and the depo shot and hated the affect of the hormones on my body (erratic mood swings, weight gain, etc). So I decided to try the IUD, a friend of mine got it and had no complaints herself although the guy she was seeing at the time  complained about feeling the string. So I deliberated over my options and went with paragard so I could leave all the hormones behind. I've never had children and the insertion was immensely painful. In that first month I experienced heavy bleeding and HEAVY cramps. But now I haven't had any period at all, according to my calendar I'm three weeks late. This seems like the opposite of everyone else's experiences. I've checked and the IUD hasn't  moved. The depo shot which I was on before this made me stop having periods, could that affect me still (even though my last injection was in May)? Thank you to anyone who can give me some advice or tell me they've experienced something similar.