could I be further along than I think?

Jade
This is my first pregnancy so I'm not sure what to expect.
I got my BFP last Friday 4 days before AF was due and it was a strong clear positive.. the second line appeared the same time as the control line within 30 seconds. 
According to my apps I would be due around 28th Jan.. I'm still quite early at only 4 weeks and 2 days 
I'm feeling realy sick throughout the day.. especially night time which is why I tested so early and I'm so bloated. Most of my apps tell me that I shouldn't have these symptoms until around 7/8 weeks. Could I be further along than what I think.. I don't get a dating scan until 10-12weeks