Confusing period

Hey, so I usually have fairly heavy periods and terrible cramps. I was supposed to start my period last Saturday but I started spotting last Wednesday. It was definitely old blood and I never had any cramps with it. The spotting ended last night and of ally my periods last almost a week. Pregnancy test came back negative (and protection is ALWAYS) used) but I’m still kinda confused. Any suggestions or thoughts on why it could be doing this?