??? Confused

I still haven't taken a test yet, because the app says I would only be 3weeks and 2days, and I'm not due for my period for another 4/5 days, but my boobs have been very sore, But I also have back pain on my left side and it feels like some cramping. Could this be PMS? Or possibly pregnant? I feel like it's too early to test , but I just thought  I'd ask for some feedback