Pls help!! (Missed period)

So basically I missed my period this month cuz it’s 7 days late and I haven’t really had any PMS apart from breaking out a lot, which never really happens. I’ve never missed a period so I’m a little worried.

I also looked back at my calendar and I realised my two previous periods were 19 days apart. Is that normal??

Also the week before I was meant to get my period I had these reallyyy bad pain like in my ass. They were like shooting pains sometimes going into my abdomen and it kinda felt like someone was stabbing a knife there.

I don’t think I’m pregnant but could someone please help me I don’t know what’s happening because I’ve never missed a period.