Late period

Okay, so I usually always have my period every 28 day, for 5 days. Well, this is going on 3rd month with out iud paragaurd. I'm 3 days late and no sign of blood. My boobs are sore, tummy is tender at lower abdomen, and mood swings. Every pregnancy test I have taken says negative. Even the one I took yesterday. I'm not really stressed. Idk what is going on. My weight is the same.