I think I'm pregnant

So, I think I'm pregnant. If the app is right I should be 4 weeks & 1 day. My boobs were sore for a couple of days then went away. I've had "flutter" feeling in my adbomen which I've never really had except previous pregnancies (I have two babies) the only issue I have with taking a test at home is with the previous pregnancy it never showed up on a test until I was like 8+ weeks along.. I'm also noticing that I'm extremely itchy under my neck & chest area. Help please