Missed period/ pregnancy scare

Well every month on the 9/10 I start. It's been that way for a while. I have a son. But the thing is my body's count of hcg when I'm pregnant is very low. so no pregnancy tests WILL pick up and tell me if I'm pregnant until 10 weeks at least. That's how my first was and they said it will continue to be that way. So should I be nervous.? My app is telling me I should start tomorrow but it's always the 10th day so it's seven days late.? Maybe I'm just stressing myself into an irregular period this month. Don't get me wrong I'd love to have a little girl. I just hate not knowing. Any tips?