Glow says 5w 6ds?

K • 22. mum to baby boy :)
Hi, glow says i am 5 weeks and 6 days along, i havent had a chance to see a doctor yet but making an appointment soon, how close is glow usually to what a doctor tells you you are? Is it quite close or is there a chance im not as far along as 5w? Iv also been having really sharpish pains in my lower stomach on and off with no bleeding is this ok? Thanks :)